U.S. patent application number 11/569353 was filed with the patent office on 2007-10-04 for cubic boron nitride sintered material and cutting tool using the same.
This patent application is currently assigned to KYOCERA CORPORATION. Invention is credited to Kenji Noda, Daisuke Shibata.
Application Number | 20070227297 11/569353 |
Document ID | / |
Family ID | 35522154 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070227297 |
Kind Code |
A1 |
Noda; Kenji ; et
al. |
October 4, 2007 |
Cubic Boron Nitride Sintered Material and Cutting Tool Using the
Same
Abstract
A cubic boron nitride sintered material where wear resistance is
suppressed from decreasing having excellent chipping resistance and
a cutting tool made thereof are provided. The sintered material is
constituted from cubic boron nitride particles that are bound by a
binder phase, while the binder phase contains a carbide of at least
one kind of metal element selected from among metals of groups 4, 5
and 6 of the periodic table and a nitride of at least one kind of
metal element selected from among metals of groups 4, 5 and 6 of
the periodic table coexisting therein, and therefore the particles
can be suppressed from coming off and the binder phase can be
suppressed from wearing and coming off at the same time, thereby
making the sintered material having high wear resistance and
particularly excellent chipping resistance.
Inventors: |
Noda; Kenji;
(Satsumasendai-shi, JP) ; Shibata; Daisuke;
(Satsumasendai-shi, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
1999 AVENUE OF THE STARS
SUITE 1400
LOS ANGELES
CA
90067
US
|
Assignee: |
KYOCERA CORPORATION
6, Takeda Tobadono-cho, Fushimi-ku
Kyoto-shi, Kyoto
JP
612-8501
|
Family ID: |
35522154 |
Appl. No.: |
11/569353 |
Filed: |
October 26, 2005 |
PCT Filed: |
October 26, 2005 |
PCT NO: |
PCT/JP05/20061 |
371 Date: |
November 17, 2006 |
Current U.S.
Class: |
75/238 ; 423/290;
501/96.4 |
Current CPC
Class: |
C04B 35/583 20130101;
C04B 2235/3886 20130101; C04B 35/63416 20130101; Y10T 428/2918
20150115; Y10T 428/2927 20150115; B22F 2998/00 20130101; C04B 41/52
20130101; Y10T 428/2929 20150115; C04B 35/63432 20130101; C04B
41/5068 20130101; C04B 2235/404 20130101; C04B 41/52 20130101; C04B
35/5831 20130101; C04B 2235/524 20130101; C04B 2237/36 20130101;
Y10T 428/2964 20150115; C04B 41/89 20130101; C04B 35/62868
20130101; B23B 2240/08 20130101; C04B 2235/3813 20130101; C04B
41/52 20130101; C04B 2235/785 20130101; B23B 2226/125 20130101;
C04B 2235/6581 20130101; C04B 2235/80 20130101; C04B 2237/704
20130101; C04B 35/63408 20130101; C04B 41/009 20130101; C04B
2235/5436 20130101; C04B 2235/3856 20130101; C04B 2235/786
20130101; C04B 35/581 20130101; C04B 41/5068 20130101; C04B
2235/3804 20130101; C04B 2235/3865 20130101; C04B 2235/402
20130101; C04B 2237/361 20130101; C04B 2235/6565 20130101; C04B
35/645 20130101; C22C 2026/006 20130101; Y10T 428/2916 20150115;
C04B 2237/363 20130101; C04B 2235/6562 20130101; C04B 2235/428
20130101; C04B 35/58014 20130101; C04B 2235/5445 20130101; C04B
2235/96 20130101; C22C 29/16 20130101; C04B 41/4529 20130101; C04B
41/5061 20130101; C04B 41/5068 20130101; C04B 41/524 20130101; C04B
41/4529 20130101; C04B 35/5831 20130101; C04B 41/4529 20130101;
C04B 41/522 20130101; C04B 41/5133 20130101; C04B 41/4529 20130101;
C04B 41/455 20130101; C04B 41/5031 20130101; C04B 41/4529 20130101;
C04B 41/455 20130101; C04B 41/4529 20130101; C04B 41/5068 20130101;
C04B 41/5063 20130101; C04B 2235/6567 20130101; C04B 41/5068
20130101; C04B 35/63488 20130101; C04B 2235/3847 20130101; C04B
35/58021 20130101; B23B 27/148 20130101; C04B 41/009 20130101; C04B
41/52 20130101; C22C 26/00 20130101; C04B 35/58 20130101; C04B
2235/6021 20130101; B22F 2998/00 20130101; C04B 41/87 20130101;
C04B 2235/3839 20130101; C04B 2237/52 20130101; C04B 35/632
20130101; Y10T 428/2913 20150115; C04B 35/584 20130101; C04B 41/52
20130101; Y10T 428/2933 20150115; C04B 2235/656 20130101; C04B
35/63424 20130101; C04B 2237/38 20130101; B32B 18/00 20130101; C04B
2235/3843 20130101; C04B 2235/405 20130101 |
Class at
Publication: |
075/238 ;
423/290; 501/096.4 |
International
Class: |
C04B 35/5831 20060101
C04B035/5831; B23B 27/14 20060101 B23B027/14; C04B 35/622 20060101
C04B035/622; C22C 29/00 20060101 C22C029/00; B32B 18/00 20060101
B32B018/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 28, 2004 |
JP |
2004-314592 |
Feb 24, 2005 |
JP |
2005-049771 |
Mar 29, 2005 |
JP |
2005-095855 |
Mar 29, 2005 |
JP |
2005-095857 |
Mar 29, 2005 |
JP |
2005-096111 |
Claims
1. A cubic boron nitride sintered material constituted from cubic
boron nitride particles that are bound by a binder phase, wherein
said binder phase contains a carbide of at least one kind of metal
element selected from among metals of groups 4, 5 and 6 of the
periodic table and a nitride of at least one kind of metal element
selected from among metals of groups 4, 5 and 6 of the periodic
table coexisting therein.
2. A cubic boron nitride sintered material having such a
single-filament fiber-like structure that a shell member made of
the cubic boron nitride sintered material constituted from cubic
boron nitride particles that are bound by a binder phase made of
nitride of at least one kind of metal element selected from among
metals of groups 4, 5 and 6 of the periodic table covers the
circumferential surface of a fiber-like core member made of the
cubic boron nitride sintered material constituted from cubic boron
nitride particles that are bound by a binder phase made of carbide
of at least one kind of metal element selected from among metals of
groups 4, 5 and 6 of the periodic table.
3. A cubic boron nitride sintered material having such a
single-filament fiber-like structure that a shell member made of
the cubic boron nitride sintered material constituted from cubic
boron nitride particles that are bound by a binder phase made of
carbide of at least one kind of metal element selected from among
metals of groups 4, 5 and 6 of the periodic table covers the
circumferential surface of a fiber-like core member made of the
cubic boron nitride sintered material constituted from cubic boron
nitride particles that are bound by a binder phase made of nitride
of at least one kind of metal element selected from among metals of
groups 4, 5 and 6 of the periodic table.
4. The cubic boron nitride sintered material according to claim 2
or 3, which has a multi-filament fiber-like structure constituted
from a plurality of said single-filament fiber-like structure
bundled together.
5. The cubic boron nitride sintered material according to any one
of claims 1 to 3, wherein the metal element that constitutes said
carbide and the metal element that constitutes said nitride are the
same metal element.
6. The cubic boron nitride sintered material according to claim 5,
wherein said metal element is titanium.
7. The cubic boron nitride sintered material according to any one
of claims 1 to 3, wherein a ratio (P.sub.C/P.sub.N) of the
proportion of the content P.sub.C of the carbide in the entire
cubic boron nitride sintered material to the proportion of the
content P.sub.N of the nitride is in a range from 0.2 to 3.0.
8. The cubic boron nitride sintered material according to any one
of claims 1 to 3, wherein such an the intermediate phase is
provided on the circumference of said cubic boron nitride
particles, that contains a compound, other than the component of
said binder phase, which is one of carbide, nitride, carbonitride,
boride, borocarbide, boronitride and oxide of at least one metal
element selected from among metals of groups 4, 5 and 6 of the
periodic table, iron group metals and Al.
9. The cubic boron nitride sintered material according to claim 8,
wherein the proportion of the content P.sub.cBN of said cubic boron
nitride particles to the entire cubic boron nitride sintered
material is in a range from 45 to 80% by area, the proportion of
the content P.sub.C of said carbide is in a range from 2 to 45% by
area, the proportion of the content P.sub.N of said nitride is in a
range from 3 to 50% by area, and the proportion of the content
P.sub.m of said intermediate phase is in a range from 0 to 25% by
area.
10. The cubic boron nitride sintered material according to any one
of claims 1 to 3, wherein the proportion of the content of
carbonitride that is a solid solution of said carbide and said
nitride to the entire cubic boron nitride sintered material is 5%
by weight or less.
11. The cubic boron nitride sintered material according to any one
of claims 1 to 3, wherein a peak attributed to said nitride and a
peak attributed to said carbide coexist in X-ray diffraction
analysis.
12. The cubic boron nitride sintered material according to claim
11, wherein a ratio (I.sub.C/I.sub.N) of the intensity I.sub.C of a
diffraction peak attributed to (200) plane of said carbide to the
intensity I.sub.N of a diffraction peak attributed to (200) plane
of said nitride is in a range from 0.2 to 1.2 in said X-ray
diffraction analysis.
13. The cubic boron nitride sintered material according to claim
11, wherein a ratio (I.sub.N/I.sub.cBN) of the intensity I.sub.N of
a diffraction peak of said nitride to the intensity I.sub.cBN of a
diffraction peak attributed to (111) plane of said cubic boron
nitride particles is in a range from 0.3 to 1 in said X-ray
diffraction analysis.
14. The cubic boron nitride sintered material according to claim
11, wherein a ratio (I.sub.C/I.sub.cBN) of the intensity I.sub.C of
a diffraction peak of said carbide to intensity I.sub.cBN of a
diffraction peak attributed to (111) plane of said cubic boron
nitride particles is in a range from 0.1 to 0.9 in said X-ray
diffraction analysis.
15. The cubic boron nitride sintered material according to claim
11, wherein the intensity I.sub.CN of a diffraction peak attributed
to (200) plane of carbonitride, that is a solid solution of said
carbide and said nitride, and the peak intensities I.sub.C and
I.sub.N satisfy relationships of I.sub.CN<0.3 I.sub.C and
I.sub.CN<0.3 I.sub.N in said X-ray diffraction analysis.
16. The cubic boron nitride sintered material according to claim
11, wherein a ratio (I.sub.IL/I.sub.cBN) of the intensity I.sub.IL
of a diffraction peak attributed to (101) plane of said
intermediate phase to intensity I.sub.cBN of a diffraction peak
attributed to (111) plane of the cubic boron nitride particles is
in a range from 0.1 to 0.8 in said X-ray diffraction analysis.
17. The cubic boron nitride sintered material according to any one
of claims 1 to 3, wherein a ratio (d.sub.N/d.sub.C) of the mean
particle size d.sub.N calculated from equivalent circles
corresponding to areas of individual grains of said nitride to the
mean particle size d.sub.C calculated from equivalent circles
corresponding to areas of individual grains of said carbide located
between the cubic boron nitride particles, measured by observing
the cross section of the cubic boron nitride sintered material, is
in a range from 0.4 to 1.2.
18. The cubic boron nitride sintered material according to claim 17
wherein the mean particle size d.sub.cBN determined from equivalent
circles corresponding to areas of individual cubic boron nitride
particles is 5 .mu.m or smaller, the mean particle size d.sub.C of
said carbide is in a range from 1 to 3 .mu.m and the mean particle
size d.sub.N of said nitride is in a range from 0.5 to 2 .mu.m, as
determined through observation of cross section of said cubic boron
nitride sintered material.
19. The cubic boron nitride sintered material according to any one
of claims 1 to 3, wherein the residual compressive stress
.sigma..sub.cBN of 300 MPa or more remains on said cubic boron
nitride particles.
20. The cubic boron nitride sintered material according to claim
19, wherein the residual compressive stress .sigma..sub.b remains
in said binder phase and ratio (.sigma..sub.cBN/.sigma..sub.b) of
the residual compressive stress .sigma..sub.cBN to the residual
compressive stress .sigma..sub.b is in a range from 2 to 5.
21. The cubic boron nitride sintered material according to claim
20, wherein the residual compressive stress .sigma..sub.b remaining
in said binder phase is in a range from 60 to 300 MPa.
22. The cubic boron nitride sintered material according to claim
19, wherein the ratio (.sigma..sub.C/.sigma..sub.N) of the residual
compressive stress .sigma..sub.C acting on said carbide to the
residual compressive stress .sigma..sub.N acting on said nitride in
said binder phase in a range from 1.5 to 5.
23. The cubic boron nitride sintered material according to claim
22, wherein the residual compressive stress .sigma..sub.N acting on
said nitride is in a range from 30 to 200 MPa and the residual
compressive stress ac acting on said carbide is in a range from 100
to 700 MPa.
24. The cubic boron nitride sintered material according to any one
of claims 1 to 3, wherein the surface of said cubic boron nitride
sintered material is coated with at least one layer of a hard film
constituted from at least one kind of carbide, nitride, boride,
oxide and carbonitride of at least one metal element selected from
among the metals of groups 4, 5 and 6 of the periodic table, Al and
Si and solid solution thereof, hard carbon and boron nitride.
25. The cubic boron nitride sintered material according to claim
24, wherein said hard film is formed by physical vapor deposition
(PVD) method.
26. The cubic boron nitride sintered material according to claim
24, wherein total thickness of said hard film is in a range from
0.1 to 15 .mu.m.
27. The cubic boron nitride sintered material according to claim
24, wherein the residual compressive stress remaining in said hard
film is in a range from 0.1 to 30 GPa.
28. The cubic boron nitride sintered material according to claim
24, wherein the residual compressive stress of the cubic boron
nitride sintered material in the state of being coated with said
hard film is 200 MPa or higher.
29. The cubic boron nitride sintered material according to claim
24, wherein at least one layer of said hard film is formed from a
compound represented by the following general formula (1):
[Chemical Formula 3]
[Ti.sub.a,M.sub.1-a][B.sub.xC.sub.yN.sub.zO.sub.1-(x+y+z)] (1)
wherein M represents at least one kind of metal element selected
from among elements, except for Ti, of groups 4, 5 and 6 of the
periodic table, Al and Si, 0<a .ltoreq.1, 0 .ltoreq.x.ltoreq.1,
0.ltoreq.y.ltoreq.1 and 0.ltoreq.z.ltoreq.1.
30. The cubic boron nitride sintered material according to claim 29
wherein at least one layer of said hard film is formed from a
compound represented by the following general formula (2):
[Chemical Formula 4]
[Ti.sub.a,M.sub.1-a][B.sub.xC.sub.yN.sub.zO.sub.1-(x+y+z)] (2)
wherein M represents at least one kind of metal element selected
from among elements, except for Ti, of groups 4, 5 and 6 of the
periodic table, Al and Si, 0.3.ltoreq.a.ltoreq.0.7, 0.ltoreq.x
.ltoreq.0.5, 0.ltoreq.y.ltoreq.0.5, 0.5.ltoreq.z.ltoreq.1 and
x+y+z.ltoreq.1.
31. The cubic boron nitride sintered material according to claim
24, wherein a ratio [I.sub.(111)/I.sub.(200)] of the intensity
I.sub.(111) of a diffraction peak attributed to (111) plane to the
intensity I.sub.(200) of a diffraction peak attributed to (200)
plane measured in X-ray diffraction analysis of at least one layer
of said hard film is 0.7 or higher.
32. A cutting tool made of the cubic boron nitride sintered
material according to any one of claims 1 to 3, that is used in
cutting operation by pressing a cutting edge, formed along a ridge
where a flank and a rake face thereof meet, against a workpiece to
be cut.
33. The cutting tool according to claim 32 comprising a tool body
and a tool tip brazed onto a mounting seat of said tool body,
wherein the tool tip is made of said cubic boron nitride sintered
material.
34. A method for manufacturing the cutting tool according to claim
32 that is used in cutting operation by pressing the cutting edge,
formed along the ridge where said flank and said rake face thereof
meet, against a workpiece to be cut.
Description
TECHNICAL FIELD
[0001] The present invention relates to a cubic boron nitride
sintered material constituted from cubic boron nitride particles
bound by a binding phase and to a cutting tool that uses the
same.
BACKGROUND ART
[0002] Cubic boron nitride (cBN) is characterized by a high
hardness next only to diamond, and yet not having reactivity with
ferrous metals unlike diamond. Accordingly, cubic boron nitride
sintered material (cBN sintered material) is used in tools for
cutting ferrous materials, especially hardened steel and cast
iron.
[0003] When a cutting tool is made of cBN sintered material, for
example, cBN sintered material made by sintering cBN under an
ultra-high pressure has been used with a metal such as cobalt (Co)
and ceramics such as titanium carbide (TiC) contained as binder in
a concentration from 10 to 60% by volume, according to Patent
Document 1. It is also proposed in Patent Document 1 to keep the
binder phase to a minimum amount and form such a structure that cBN
of the rest is directly bonded with each other, in order to avoid
compromising wear resistance and heat resistance of the cBN
sintered material.
[0004] Recently, in the field of metal cutting, there are demands
to increase the efficiency of cutting operation and provide the
capability to machine hard-to-cut materials. And cBN sintered
material is also required to improve wear resistance and chipping
resistance, as the basic requirements. Patent Document 2 proposes a
cBN sintered material wherein cBN particles are bound by a large
amount of binder constituted from ceramics such as titanium
carbonitride (TiCN), an intermetallic compound of Ti and Al and
tungsten carbide (WC) for the purpose of improving the properties
described above.
[0005] [Patent Document 1] Japanese Examined Patent Publication
(Kokoku) No. 52-43846
[0006] [Patent Document 2] Japanese Unexamined Patent Publication
(Kokai) No. 2003-175407
DISCLOSURE OF THE INVENTION
[Problems to be Solved by the Invention]
[0007] However, when hardened steel or cast iron is cut with a
cutting tool made from the cBN sintered material described in
Patent Document 1, there has been such a problem that cBN particles
come off from the sintered body during the cutting operation, thus
causing wear of the cutting tool to proceed significantly.
[0008] With the method of adding a large amount of binder described
in Patent Document 2, there have been such problems that, though it
is made possible to restrict the cBN particles from coming off and
wear from rapidly proceeding, the binder phase constituted from
titanium carbonitride (TiCN), the intermetallic compound of Ti and
Al and tungsten carbide (WC) has lower mechanical property and
lower thermal property. As a result, wear and fall-off of the
binder phase become conspicuous and cause wear and chipping of the
tool, thus making it impossible to elongate the tool life.
[0009] An object of the present invention is to provide a cBN
sintered material that is capable of restricting wear resistance
from decreasing and has excellent chipping resistance, and a
cutting tool that uses the same.
[Means for Solving the Problems]
[0010] The present inventors made a research to solve the problems
of progress in wear and chipping of the tool at the same time.
Through the research, it was found that a cBN sintered material
constituted from cBN particles that are bound by a binder phase,
when the binder phase contains a carbide of a particular metal
element and a nitride of a particular metal element coexisting
therein, shows excellent properties that cannot be achieved by
using a binder phase constituted from a carbide, a nitride or a
carbonitride that is a solid solution thereof. It was also found
that the cBN sintered material having such a constitution is
capable of suppressing the cBN particles from coming off and the
binder phase from wearing and coming off at the same time, thus
exhibiting high wear resistance and, especially, excellent chipping
resistance, thus completing the present invention.
[0011] Specifically, the cBN sintered material of the present
invention is a cBN sintered material constituted from cBN particles
that are bound by a binder phase, wherein the binder phase contains
a carbide of at least one kind of metal element selected from among
a group consisting of groups 4, 5 and 6 of the periodic table and a
nitride of at least one kind of metal element selected from among a
group consisting of groups 4, 5 and 6 of the periodic table
coexisting therein.
[0012] Another cBN sintered material of the present invention has
such a single-filament fiber-like structure that a shell member
made of the cBN sintered material constituted from cBN particles
that are bound by a binder phase made of nitride of at least one
kind of metal element selected from among a group consisting of
groups 4, 5 and 6 of the periodic table covers the circumferential
surface of a fiber-like core member made of the cBN sintered
material constituted from cBN particles that are bound by a binder
phase made of carbide of at least one kind of metal element
selected from among a group consisting of groups 4, 5 and 6 of the
periodic table.
[0013] Further another cBN sintered material of the present
invention has such a single-filament fiber-like structure that a
shell member made of cBN sintered material constituted from cBN
particles that are bound by a binder phase made of carbide of at
least one kind of metal element selected from among a group
consisting of groups 4, 5 and 6 of the periodic table covers the
circumferential surface of a fiber-like core member made of cBN
sintered material constituted from cBN particles that are bound by
binder phase made of nitride of at least one kind of metal element
selected from among a group consisting of groups 4, 5 and 6 of the
periodic table.
[0014] The cutting tool of the present invention is made of the cBN
sintered material of the present invention described above, and is
used in metal cutting operations with a cutting edge, that is
formed along a ridge where a flank and a rake face thereof meet,
pressed against a workpiece to be cut.
Effects of the Invention
[0015] The cBN sintered material of the present invention is
characterized principally by the fact that a carbide of a
particular metal element and a nitride of a particular metal
element coexist therein. This enables it to achieve both a level of
strength of the binder phase and a level of bonding force between
the binder phase and the cBN particles, that cannot be obtained
with the conventional sintered material that uses the binder phase
constituted from a carbide, a nitride or a carbonitride that is a
solid solution thereof. As a result, it is made possible to
suppress the cBN particles from coming off and the binder phase
from wearing and coming off at the same time, thus providing the
cBN sintered material having high wear resistance and greatly
improved chipping resistance.
[0016] In consequence, the cBN sintered material and the cutting
tool of the present invention are capable of, as well as cutting
operations under normal conditions, interrupted cutting of
hard-to-cut materials such as hardened steel with excellent wear
resistance and chipping resistance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1(a) is a schematic diagram showing the structure of
the cBN sintered material of the present invention, and FIG. 1(b)
is a schematic diagram showing the structure of the cBN sintered
material having a binder phase of uniform composition.
[0018] FIG. 2 is an X-ray diffraction analysis chart of the cBN
sintered material of the present invention showing the diffraction
peaks.
[0019] FIG. 3 is a schematic sectional view showing cBN sintered
material according to a fifth embodiment.
[0020] FIG. 4(a) is a schematic sectional view showing the cBN
sintered material having single-filament fiber-like structure of
the present invention, and FIG. 4(b) is a perspective view of
(a).
[0021] FIG. 5(a) is a schematic sectional view showing the cBN
sintered material having multi-filament fiber-like structure of the
present invention, and FIG. 5(b) is a perspective view of (a).
[0022] FIGS. 6(a) to 6(d) are schematic perspective views showing
examples of arranging the cBN sintered material having fiber-like
structure of the present invention.
[0023] FIGS. 7(a) and 7(b) are schematic diagrams showing a method
of manufacturing a composite green compact according to the method
of manufacturing the cBN sintered material having single-filament
fiber-like structure of the present invention.
[0024] FIG. 8 is a schematic diagram showing a method of
manufacturing a green compact according to the method of
manufacturing the cBN sintered material having multi-filament
fiber-like structure of the present invention.
[0025] FIG. 9 is a schematic diagram showing a method of
manufacturing a green compact having another form according to the
method of manufacturing the cBN sintered material having
multi-filament fiber-like structure of the present invention.
[0026] FIG. 10 is a perspective view showing an embodiment of the
cutting tool according to the present invention.
[0027] FIG. 11(a) is a schematic sectional view showing an example
of the structure of a tool tip corner of the present invention, and
FIG. 11(b) is a schematic sectional view showing another
example.
DESCRIPTION OF REFERENCE NUMERALS
[0028] 1 cBN sintered material [0029] 2 cBN particles [0030] 3
Binder phase [0031] 4 Intermediate phase [0032] 5 Carbide [0033] 6
Nitride [0034] 7 Carbonitride [0035] 8 Fiber-like core member made
of cBN sintered material [0036] 8a Fiber-like core member made of
cBN sintered material (Binder phase is formed from carbide.) [0037]
8b Fiber-like core member made of cBN sintered material (Binder
phase is formed from nitride.) [0038] 9 Shell member made of cBN
sintered material [0039] 9a Shell member made of cBN sintered
material (Binder phase is formed from nitride.) [0040] 9b Shell
member made of cBN sintered material (Binder phase is formed from
carbide.) [0041] 10 cBN sintered material having single-filament
fiber-like structure [0042] 10a First cBN sintered material [0043]
10b Second cBN sintered material [0044] 11 cBN sintered material
having multi-filament fiber-like structure [0045] 12 Tool tip
[0046] 13 Tool insert [0047] 14 Cutting edge [0048] 15 Backing
member [0049] 16 Sheet-like structure [0050] 16A Composite cBN
sintered material arranged in sheet-like configuration [0051] 16B
Sheet-like arrangement of 16A stacked with fibers in parallel
[0052] 16C Sheet-like arrangement of 16A stacked with fibers
perpendicular to each other [0053] 16D Sheet-like arrangement of
16A stacked with fibers perpendicular to sheet surface [0054] 17
Green compact of core member [0055] 18 Green compact of shell
member [0056] 19 Composite green compact [0057] 20 Composite green
compact having single-filament fiber-like structure [0058] 21
Composite green compact having multi-filament fiber-like structure
[0059] 22 Composite green compact having sheet shape [0060] 23 Roll
[0061] 30 cBN sintered material for cutting tool [0062] 31 Rake
face [0063] 32 Flank face [0064] 40 Hard coating film [0065]
I.sub.cBN Highest peak in X-ray diffraction analysis of cBN
particles [0066] I.sub.N Peak intensity of nitride from (200) plane
in X-ray diffraction analysis [0067] I.sub.c Peak intensity of
carbide from (200) plane in X-ray diffraction analysis [0068]
d.sub.c Diameter of core member [0069] d.sub.s Thickness of shell
member
Mode for Carrying Out the Invention
[0069] <cBN Sintered Material>
[0070] Preferred embodiments of the cBN sintered material according
to the present invention will now be described in detail with
reference to the accompanying drawings.
FIRST EMBODIMENT
[0071] FIG. 1(a) is a schematic diagram showing the structure of
the cBN sintered material according to first embodiment of the
present invention. As shown in FIG. 1(a), the cBN sintered material
1 consists of cBN particles 2 (black portions in FIG. 1(a)) and a
binder phase 3. Specifically, the cBN sintered material 1 is
constituted from the cBN particles 2 that constitute the hard phase
bound together by the surrounding binder phase 3. The cBN sintered
material also has an intermediate phase 4 disposed between the cBN
particles 2 and the binder phase 3, for binding the cBN particles 2
and the binder phase 3.
[0072] In the binder phase 3 of this embodiment, carbide 5 of at
least one kind of metal element selected from among a group
consisting of groups 4, 5 and 6 of the periodic table and nitride 6
of at least one kind of metal element selected from among a group
consisting of groups 4, 5 and 6 of the periodic table coexist. When
the binder phase 3 is made in this constitution, it is made
possible to increase the strength of the binder phase 3 and
increase the bonding force between the binder phase and the cBN
particles 2 at the same time, and also generate residual stress
between the binder phase 3 and the cBN particles 2 thereby ensuring
firm binding between the cBN particles 2. As a resuLt, it is made
possible to suppress the cBN particles 2 from coming off and the
binder phase from wearing, thus providing the cBN sintered material
1 having high wear resistance and, especially, excellent chipping
resistance. The phrase that the carbide 5 and the nitride 6 coexist
means the state of the carbide 5 and the nitride 6 exist
independently from each other in the binder phase 3.
[0073] In case the binder phase 3 has a uniform composition of
carbonitride 7 that is a solid solution of carbide and nitride as
shown in FIG. 1(b), it is not possible to increase the strength of
the binder phase and increase the bonding force between the binder
phase and the cBN particles 2 at the same time. In case the binder
phase 3 is constituted from the carbide 5 only, on the other hand,
bonding force between the binder phase 3 and the cBN particles 2
decreases, thus resulting in sintering failure or fall-ff of the
cBN particles 2. This leads to breakage or chipping when subjected
to impact. In case the binder phase 3 is constituted from the
nitride 6 only, on the other hand, wear resistance decreases
significantly.
[0074] In the case of a structure formed from the combination of
the core member and the shell member as in the case of the cBN
sintered materials 10, 11 of fiber-like structure to be described
later, properties of the core member and the shell member can be
put into action in a well-balanced manner by making one of the
binder phases of the core member and the shell member from carbide
and the other from nitride, thus causing the cBN sintered material
10, 11 to exhibit the best performance.
[0075] Coexistence of the carbide 5 and the nitride 6 in the binder
phase 3 may be confirmed by, for example, polishing the cBN
sintered material 1 in mirror finish and observing the polished
surface under a metallurgical microscope with magnification factor
of 100 to 1000. When titanium, for example, is used as the metal
element to form the carbide 5 and the nitride 6, the brightest
portions represent the carbide 5 and the darkest portions represent
the cBN particles 2, while portions having intermediate brightness
representing the nitride 6.
[0076] Coexistence of the carbide 5 and the nitride 6 in the binder
phase 3 may also be confirmed by mapping the component analysis. In
case EPMA (electron probe microanalysis) is carried out by using a
WDS (wavelength-dispersion type X-ray spectrometer), for example,
coexistence of the carbide 5 and the nitride 6 can be confirmed by
mapping carbon, nitrogen, boron and metal elements. Various regions
may also be determined whether they consist of carbide 5 or nitride
6 by the X-ray photoelectron spectroscopy (ESCA). In addition,
X-ray diffraction analysis to be described later may also be used
to effectively confirm the coexistence of the carbide and the
nitride.
[0077] The metal element that constitutes the carbide 5 and the
metal element that constitutes the nitride 6 may be different
elements, although they are preferably the same metal elements in
order to achieve high strength of the binder phase 3 and strong
bonding between the cBN particles 2. It is particularly preferable
that the metal element is titanium (Ti), so that the binder phase 3
consists of titanium carbide (TiC) and titanium nitride (TiN). In
this case, since titanium has high affinity with the cBN particles
2 so that high residual compressive stress can remain between the
cBN particles 2, bonding of the cBN particles 2 becomes stronger
thus making the material excellent in wear resistance and in
chipping resistance.
[0078] Ratio (P.sub.C/P.sub.N) of proportion P.sub.C of carbide 5
content in the cBN sintered material 1 to proportion P.sub.N of
nitride 6 content is preferably in a range from 0.2 to 3.0, more
preferably from 0.5 to 2.0, in order to achieve sufficient effect
of suppressing the cBN particles from coming off and the binder
phase 3 from wearing and coming off. When the cBN sintered material
1 is used to make a cutting tool, wear resistance can be suppressed
from decreasing during cutting operation and the cBN particles 2
can be prevented from coming off, thereby preventing excessive wear
from occurring.
[0079] It is preferable that there exists, on the circumference of
the cBN particles 2 of the cBN sintered material 1, the
intermediate phase 4 that contains a compound other than the
component of the binder phase 3, that is one of carbide, nitride,
carbonitride, boride, borocarbide, boronitride and oxide of at
least one metal element selected from among metals of groups 4, 5
and 6 of the periodic table, iron group metals and Al. This
constitution enables it to firmly hold the cBN particles 2
together. The intermediate phase 4 may be made of, for example,
TiB.sub.2, AlN or the like.
[0080] It is preferable that proportion P.sub.cBN of the cBN
particles 2 to the entire cBN sintered material 1 is in a range
from 45 to 80% by area, proportion P.sub.c of the carbide 5 is in a
range from 2 to 45% by area, proportion P.sub.N of the nitride 6 is
in a range from 3 to 50% by area, and proportion P.sub.m of the
intermediate phase 4 is in a range from 0 to 25% by area. This
makes it possible to make full use of high hardness of the carbide
5 and the binding force between the nitride 6 and the cBN particles
2. Also because this constitution has good balance of the contents
of the cBN particles 2, the binder phase 3 and the intermediate
phase 4, high hardness and high toughness can be maintained thereby
to achieve high wear resistance and high chipping resistance. The
percentage by area described above can be calculated, for example,
through image analysis of the metallurgical microscope
photograph.
[0081] It is also preferable that proportion of the carbonitride
content that is a solid solution of carbide 5 and nitride 6 is 5%
by weight or less of the entire cBN sintered material 1. This
increases the proportion of the cBN particles 2 and decreases the
proportion of the binder phase 3, thus suppressing the cBN
particles 2 from coming off, and the binder phase 3 from wearing
and coming off. Content of carbonitride may be determined by
measuring the corresponding peak intensity in X-ray diffraction
analysis and comparing it with the calibration curve of a standard
sample prepared separately.
[0082] Mean particle size of the cBN particles 2 is preferably in a
range from 0.2 to 5.0 .mu.m, more preferably in a range from 0.5 to
3.0 .mu.m in consideration of wear resistance and strength.
[0083] An example of method for manufacturing the cBN sintered
material of this embodiment will now be described. First, stock
material powder is prepared by weighing a cBN material powder
having a mean particle size of 0.2 to 3 .mu.m, a powder of carbide
of at least one kind of metal element selected from among metals of
groups 4, 5 and 6 of the periodic table having a mean particle size
from 0.2 to 3 .mu.m, preferably from 0.5 to 3 .mu.m, more
preferably from 1 to 3 .mu.m, and a powder of nitride of at least
one kind of metal element selected from among metals of groups 4, 5
and 6 of the periodic table having a mean particle size from 0.2 to
3 .mu.m, preferably from 0.5 to 3 .mu.m, more preferably from 1 to
3 .mu.m. In addition, as required, a powder of Al or at least one
kind of iron group metals having a mean particle size from 0.5 to 5
.mu.m is weighed according to a particular composition. These
ponders are crushed and milled in a ball mill for a period of 16 to
72 hours.
[0084] Then the mixture of crushed powders is formed in a
predetermined shape. Known means can be employed in the forming
process, for example, press forming, injection molding, casting or
extrusion molding.
[0085] The green compact is charged in an ultrahigh pressure
sintering apparatus together with a backing member made of cemented
carbide that is prepared separately, and is held at a temperature
from 1200 to 1400.degree. C. under a pressure of 5 GPa for a period
of 10 to 30 minutes, thereby to obtain the cBN sintered material of
this embodiment. In order to make such a structure that a carbide
of one metal selected from among metals of groups 4, 5 and 6 of the
periodic table and a nitride of one metal selected from among
metals of groups 4, 5 and 6 of the periodic table exist
independently, it is preferable to set the rate of raising and
lowering the temperature in a range from 30 to 50.degree. C. per
minute and the duration of holding the heating temperature (firing
period) in a range from 10 to 15 minutes. When the firing
temperature, firing pressure holding period, temperature raising
rate and temperature lowering rate deviate from the ranges
described above, it becomes difficult to control the structure so
as to contain carbide and nitride coexisting therein.
SECOND EMBODIMENT
[0086] A second embodiment of the cBN sintered material according
to the present invention will now be described. In this embodiment,
components that are identical with or similar to those of the first
embodiment will be denoted with the same reference numeral and
description thereof will be omitted.
[0087] The cBN sintered material of this embodiment shows a
diffraction peak generated by the nitride 6 and a diffraction peak
generated by the carbide 5 coexisting in X-ray diffraction analysis
as shown in FIG. 1(a). Specifically as shown in FIG. 2, the cBN
sintered material is characterized by the coexistence of a
diffraction peak I.sub.N generated by nitride 6 of at least one
metal element selected from among metals of groups 4, 5 and 6 of
the periodic table (nitride peak) and a diffraction peak I.sub.C
generated by carbide 5 of at least one metal element selected from
among metals of groups 4, 5 and 6 of periodic table (carbide peak)
in X-ray diffraction analysis.
[0088] Specifically, the nitride 6 and the carbide 5 coexist with
such a level that a diffraction peak attributed to (200) plane of
nitride 6 and a diffraction peak attributed to (200) plane of
carbide 5 in the X-ray diffraction analysis. This makes it possible
to make residual stress remain between the binder phase 3 and the
cBN particles 2 shown in FIG. 1(a), make the bonding of the cBN
particles 2 stronger and prevent the cBN particles 2 from coming
off. Peak intensity I may be estimated in the present invention by
separating the peaks from the diffraction chart when the
diffraction chart is crowded with various peaks overlapping with
each other.
[0089] In this embodiment, coexistence of nitride 6 and carbide 5
means that the ratio (I.sub.C/I.sub.N) of the intensity I.sub.C of
a diffraction peak attributed to (200) plane of carbide 5 to
intensity I.sub.N of a diffraction peak attributed to (200) plane
of nitride 6 is in a range from 0.5 to 20.
[0090] It is preferable to control the ratio (I.sub.C/I.sub.N) of
the intensity I.sub.C of a diffraction peak attributed to (200)
plane of carbide 5 to intensity I.sub.N of a diffraction peak
attributed to (200) plane of nitride 6 in a range from 0.2 to 1.2,
more preferably from 0.3 to 0.9 as measured by X-ray diffraction
analysis. This enables it to prevent the cBN particles 2 from
coming off and excessive wear from occurring while preventing wear
resistance from decreasing during cutting operation.
[0091] It is also preferable to control the ratio
(I.sub.N/I.sub.cBN) of the intensity I.sub.N of a diffraction peak
attributed to nitride 6 to intensity I.sub.cBN of a diffraction
peak attributed to (111) plane of the cBN particles 2 in a range
from 0.3 to 1 as measured by the X-ray diffraction analysis
described above. This enables it to increase the bonding force
between the cBN particles 2 and the binder phase 3 and prevent the
cBN particles 2 from coming off while maintaining high hardness,
thereby to improve the impact resistance of the cBN sintered
material 1.
[0092] It is also preferable to control the ratio
(I.sub.C/I.sub.cBN) of the intensity I.sub.C of a diffraction peak
attributed to carbide 5 to the intensity I.sub.cBN of a diffraction
peak attributed to (111) plane of the cBN particles 2 in a range
from 0.1 to 0.9 as measured by X-ray diffraction analysis. This
enables it to ensure both wear resistance and chipping resistance.
Intensities of individual peaks can be determined by separating the
peaks from the X-ray diffraction analysis chart.
[0093] It is also preferable that intensity I.sub.CN of a
diffraction peak attributed to (200) plane of carbonitride 7, that
is a solid solution of carbide 5 and nitride 6, namely the peak
which appears at an intermediate angle between the peak attributed
to (200) plane of carbide 5 and the peak attributed to (200) plane
of nitride 6, and the peak intensities I.sub.C and I.sub.N
described above satisfy relationship of I.sub.CN<0.3 I.sub.C and
I.sub.CN<0.3 I.sub.N. In other words, it is desirable that the
peak of the carbonitride 7 is hardly detectable. This enables it to
suppress the bonding force between the cBN particles 2 from
decreasing and surely prevent the cBN particles 2 from coming
off.
[0094] It is also preferable to control the ratio
(I.sub.IL/I.sub.cBN) of the intensity I.sub.IL of a diffraction
peak attributed to (101) plane of the intermediate phase 4 to
intensity I.sub.cBN of a diffraction peak attributed to (111) plane
of the cBN particles 2 in a range from 0.1 to 0.8, more preferably
from 0.4 to 0.7 as measured by X-ray diffraction analysis. This
enables it to hold the cBN particles 2 more firmly and achieve
well-balanced proportions of the contents of the cBN particles 2
and the binder phase 3 that ensure high hardness and high
toughness.
THIRD EMBODIMENT
[0095] A third embodiment of the cBN sintered material according to
the present invention will now be described. In this embodiment,
components that are identical with or similar to those of the first
and second embodiments will be denoted with the same reference
numeral and description thereof will be omitted.
[0096] In the cBN sintered material of this embodiment, the nitride
6 and the carbide 5 coexist in the binder phase 3 shown in FIG.
1(a). Mean particle size d.sub.c, calculated by averaging the
diameters of equivalent circles corresponding to areas of
individual grains of carbide 5 located between the cBN particles 2,
measured by observing the cross section of the cBN sintered
material, and mean particle size d.sub.N, calculated by averaging
the diameters of equivalent circles corresponding to areas of
individual grains of nitride 6 are such that the ratio
(d.sub.N/d.sub.C) is in a range from 0.4 to 1.2. This constitution
enables it to prevent the cBN particles 2 from coming off more
effectively, that has been impossible with the binder phase
constituted from a carbide, a nitride or a carbonitride that is a
solid solution thereof. As a result, it is made possible to
suppress the cBN particles from coming off and the binder phase 3
from wearing and coming off at the same time, thus providing the
cBN sintered material having high wear resistance and greatly
improved chipping resistance.
[0097] The mean particle size in this embodiment is determined as
follows. Locations of the compounds such as nitride 6 and carbide 5
are identified by microscopic observation of the cBN sintered
material, mean areas of the nitride 6 and carbide 5 are determined
by Luzex method or the like, and the diameter of a circle having
the area equal to the mean area becomes the mean particle size of
the nitride 6 or the carbide 5. Microscopic observation may be
carried out by using a metallurgical microscope, laser microscope,
digital microscope, scanning electron microscope, transmission
electron microscope or any appropriate microscope depending on the
constitution of the cBN sintered material.
[0098] It is preferable that the mean particle size d.sub.cBN of
the cBN particles 2 is 5 .mu.m or smaller, the mean particle size
d.sub.C of the carbide 5 is in a range from 1 to 3 .mu.m and the
mean particle size d.sub.N of the nitride 6 is in a range from 0.5
to 2 .mu.m. This improves the hardness of the cBN sintered material
and makes the bonding between the cBN particles 2 more firmly,
thereby improving the wear resistance.
Fourth Embodiment
[0099] A fourth embodiment of the cBN sintered material according
to the present invention will now be described. In this embodiment,
components that are identical with or similar to those of the first
to third embodiments will be denoted with the same reference
numeral and description thereof will be omitted.
[0100] In the cBN sintered material of this embodiment, residual
compressive stress .sigma..sub.cBN of 300 MPa or more, preferably
from 300 to 1000 MPa and more preferably from 500 to 700 MPa
remains on the cBN particles 2 shown in FIG. 1(a). This enables it
to prevent the cBN particles 2 from coming off more effectively,
improve wear resistance and greatly improve chipping
resistance.
[0101] It is preferable that residual compressive stress remains in
both the cBN particles 2 and the binder phase 3, and a ratio
(.sigma..sub.cBN/.sigma..sub.b) of the residual compressive stress
.sigma..sub.cBN remaining in the cBN particles 2 and the residual
compressive stress .sigma..sub.b remaining in the binder phase 3 is
in a range from 2 to 5, more preferably 2 to 3. This enables it to
prevent the cBN particles 2 from coming off more effectively and
increase the strength of the cBN sintered material. Wear resistance
can also be improved when ratio (.sigma..sub.cBN/.sigma..sub.b) is
from 2 to 3.
[0102] Residual compressive stress can be determined by, for
example, X-ray residual stress measuring method
(2.theta.-sin.sup.2.phi.) through X-ray diffraction analysis (XRD)
of the sintered material 1. In case the cBN sintered material 1
contains two or more kinds of material such as carbide 5 and
nitride 6 as the binder phase 3, residual stress in the binder
phase 3 is determined by taking into consideration the proportions
of the contents of carbide 5 and nitride 6. Specifically, residual
stress is determined for each material. Proportions of the contents
of these materials are also calculated by assuming that the maximum
peak intensity of X-ray diffraction analysis is proportional to the
content. Then the residual stress of each material multiplied by
the proportion of its content (the ratio of the amount of the
material to the total amount of the binder phase) is added for all
materials, thus giving the residual stress of the binder phase
3.
[0103] Residual compressive stress .sigma..sub.b remaining in the
binder phase 3 is preferably in a range from 60 to 300 MPa, more
preferably from 100 to 300 MPa. This enables it to prevent the cBN
particles 2 from coming off while improving the wear resistance and
greatly improving the chipping resistance.
[0104] Ratio (.sigma.C/.sigma..sub.N) of the residual compressive
stress .sigma..sub.C acting on the carbide 5 to the residual
compressive stress .sigma..sub.N acting on the nitride 6 in the
binder phase 3 is preferably in a range from 1.5 to 5. This enables
it to optimize the residual stress of the cBN sintered material 1
and improve wear resistance and chipping resistance of the cBN
sintered material 1.
[0105] It is also preferable that the residual compressive stress
.sigma..sub.N acting on the nitride 6 is in a range from 30 to 200
MPa and the residual compressive stress ac acting on the carbide 5
is in a range from 100 to 700 MPa, and that the value of ratio
(.sigma..sub.C/.sigma..sub.N) is within the range described
above.
FIFTH EMBODIMENT
[0106] A fifth embodiment of the cBN sintered material according to
the present invention will now be described. In this embodiment,
components that are identical with or similar to those of the first
to fourth embodiments will be denoted with the same reference
numeral and description thereof will be omitted.
[0107] FIG. 3 is a schematic sectional view showing the cBN
sintered material of this embodiment. As shown in FIG. 3, the cBN
sintered material A of this embodiment is the cBN sintered material
1 that is coated with a particular hard film 40 formed on the
surface thereof. In other words, the cBN sintered material A has
such a constitution as the cBN sintered material 1 comprising the
cBN particles 2 and binder phase 3 that contains carbide 5 and the
nitride 6 is coated with the particular hard film 40 described
above.
[0108] In this constitution, coexistence of the carbide 5, and the
nitride 6 in the binder phase 3 has such an effect that residual
compressive stress remains in the cBN sintered material 1 upon
completion of sintering due to differences in the thermal expansion
and in shrinkage between the carbide 5 and the nitride 6, so as to
improve the strength of the cBN sintered material 1. In the cBN
sintered material A of this embodiment, since the cBN sintered
material 1 is coated with the particular hard film 40 on the
surface thereof, the cBN sintered material 1 is further subjected
to the residual stress so that a high residual compressive stress
can be generated near the interface between the hard film 40 and
the cBN sintered material 1, due to the synergy effect of the
residual compressive stresses of carbide 5 and nitride 6. As a
result, residual stress on the surface of the hard film 40 can be
reduced, so that the cBN sintered material A can have very high
toughness. Moreover, since the hard film 40 has high hardness, wear
resistance can be improved further. Also because the hard film 40
is excellent in hardness at high temperatures, in oxidation
resistance and in lubricating property, it demonstrates excellent
wear resistance and chipping resistance under harsh conditions
where cutting tools and anti-wear materials are used.
[0109] The hard film 40 is constituted from at least one layer of
hard material made of carbide, nitride, boride, oxide and
carbonitride of at least one metal element selected from among the
metals of groups 4, 5 and 6 of the periodic table, Al and Si and
solid solution thereof, hard carbon and boron nitride. FIG. 3 shows
a case where the hard film 40 consists of two layers.
[0110] Preferable examples of the hard film 40 include a
single-layer film selected from among a group consisting of a film
made of a compound of Ti, Al.sub.2O.sub.3 film, polycrystalline
diamond film, diamond-like carbon (DLC) film, cubic boron nitride
(cBN) film, or a film consisting of two or more layers.
[0111] The hard film 40 may be formed by a thin film forming method
such as thermal CVD, plasma CVD or other chemical vapor deposition
method, ion plating, arc ion plating, sputtering, vapor deposition
or other physical vapor deposition method (PVD) or plating method,
to a predetermined thickness over a particular region including a
cutting edge or over the entire surface of the cBN sintered
material 1. Specifically, in case a (Ti, Al)N hard film is formed
by arc ion plating method, titanium-aluminum (TiAl) alloy is used
as a target to vaporize and ionize a metal source by arc discharge,
so that the metal ion reacts with the nitrogen (N.sub.2) gas used
as a nitrogen source to form a film. It is preferable to form the
film while applying a bias voltage of 30 to 300 V in order to
increase the density and bonding with the substrate of the film.
Conditions of the X-ray diffraction peaks of the hard film can be
controlled with predetermined range described later, by varying the
kind of gas and gas pressure when forming the film.
[0112] The hard film 40 is preferably formed by physical vapor
deposition (PVD) method. This makes it possible to improve the
bonding strength of the film with the cBN sintered material 1 and
optimize the residual stress existing on the surface of the cBN
sintered material A, thereby improving the wear resistance and
chipping resistance of the cBN sintered material A.
[0113] Total thickness of the hard film 40 is preferably in a range
from 0.01 to 15 .mu.m, more preferably from 0.1 to 10 .mu.m. This
increases the bonding strength of the hard film 40 with the cBN
sintered material 1 and makes it less likely to peel off, thereby
to suppress the film from peeling off while maintaining wear
resistance. More specifically, there exists an optimum film
thickness for each of different materials that form the hard film.
For example, a hard film of ultra-high hardness such as DLC film or
cBN film is preferably a single layer having thickness of 0.01 to
0.3 .mu.m. A hard film made of a compound of Ti to be described
later is preferably a single layer having thickness of 0.5 to 8
.mu.m. Proper residual stress of the hard film 40 is obtained with
a thickness in the range described above.
[0114] Residual compressive stress existing in the hard film 40 is
preferably in a range from 0.1 to 30 GPa. This increases the
bonding strength of the hard film 40 with the cBN sintered material
1 and optimizes the residual stress existing on the surface of the
cBN sintered material A, thereby to increase the strength of the
cBN sintered material A.
[0115] Residual compressive stress in the cBN sintered material A
coated with the hard film 40 is preferably 200 MPa or higher, more
preferably in a range from 300 to 1000 MPa and most preferably 500
to 1000 MPa. This increases the bonding strength of the hard film
40 and optimizes the residual stress existing on the surface of the
cBN sintered material A, thereby to increase the strength of the
cBN sintered material A.
[0116] It is preferable that at least one layer of the hard film 40
is made of a compound represented by the following general formula
(1). This increases the hardness and toughness of the hard film 40
and bonding strength thereof with the cBN sintered material 1.
[Chemical Formula 1]
[Ti.sub.a,M.sub.1-a][B.sub.xC.sub.yN.sub.zO.sub.1-(x+y+z)] (1)
wherein M represents at least one kind of metal element selected
from among elements, except for Ti, of groups 4, 5 and 6 of the
periodic table, Al and Si. 0<a.ltoreq.1,
0.ltoreq..times..ltoreq.1, 0.ltoreq.y.ltoreq.1 and
0.ltoreq.z.ltoreq.1.)
[0117] Moreover, it is preferable that at least one layer of the
hard film 40 is made of a compound represented by the following
general formula (2). This makes it possible to improve the
characteristics such as hardness and strength of the hard film 40,
and make the cBN sintered material A of higher toughness and higher
hardness.
[Chemical Formula 2]
[Ti.sub.a,M.sub.1-a][B.sub.xC.sub.yN.sub.zO.sub.1-(x+y+z)] (2)
wherein M represents at least one kind of metal element selected
from among elements, except for Ti, of groups 4, 5 and 6 of the
periodic table, Al and Si. 0.3.ltoreq.a.ltoreq.0.7,
0.ltoreq..times..ltoreq.0.5, 0.ltoreq.y.ltoreq.0.5,
0.5.ltoreq.z.ltoreq.1 and x+z+y+z.ltoreq.1.)
[0118] At least one layer of the hard film 40 preferably show a
value of 0.7 or higher for the ratio I.sub.(111)/I.sub.(200) of the
intensity I.sub.(111) of a diffraction peak attributed to (111)
plane to intensity I.sub.(200) of a diffraction peak attributed to
(200) plane in X-ray diffraction analysis. This makes the grain
sizes of the crystal of the compound that constitutes the hard film
40 smaller so that hardness of the hard film 40 becomes higher,
thereby to improve wear resistance. As the grains of the hard film
40 are smaller, grain defects of the hard film 40 decreases and the
bonding strength between the hard film 40 and the cBN sintered
material 1 increases, so that the film is suppressed from peeling
off with chipping resistance and thermal shock resistance being
greatly improved.
[0119] In order to increase the bonding strength between the hard
film 40 and the cBN sintered material 1, such an intermediate layer
(not shown) may be provided between the hard film 40 and the cBN
sintered material 1 that is made of a metal such as titanium, or a
nitride, carbide or carbonitride of at least one metal element
selected from among groups 4, 5 and 6 of the periodic table, B, Al
and Si.
[0120] Before forming the hard film 40, surface of the cBN sintered
material 1 may be processed by shot peening, grit blast,
electrolytic etching, chemical etching, mechanical grinding,
polishing, ion implantation or other method. Bonding strength of
the hard film 40 can also be increased by such a surface
treatment.
[0121] A cBN sintered material of fiber-like structure that is
another cBN sintered material 1 according to the first to fifth
embodiments will now be described in detail with reference to the
accompanying drawing, while taking the first embodiment as an
example. FIG. 4(a) is a schematic sectional view showing other cBN
sintered material of this embodiment, and FIG. 4(b) is a
perspective view thereof. As shown in FIGS. 4(a), 4(b), cBN
sintered material 10 has such a single-filament fiber-like
structure that a shell member 9 made of particular cBN sintered
material covers the circumferential surface of a fiber-like core
member 8 made of particular cBN sintered material.
[0122] The single-filament fiber-like structure can be made in
either of the following two forms. A first cBN sintered material
10a has such a single-filament fiber-like structure that a skin
member 9a, which is made of cBN sintered material constituted from
cBN particles 2 that are bound by a binder phase that is made of
nitride 6 of at least one kind of metal element selected from among
a group consisting of metals of groups 4, 5 and 6 of the periodic
table, covers the circumferential surface of a fiber-like core
member 8a made of cBN sintered material constituted from cBN
particles that are bound by a binder phase made of carbide 5 of at
least one kind of metal element selected from among metals of
groups 4, 5 and 6 of the periodic table.
[0123] A second cBN sintered material 10b has such a
single-filament fiber-like structure that a shell member 9b made of
cBN sintered material constituted from cBN particles 2 that are
bound by a binder phase made of carbide 5 of at least one kind of
metal element selected from among metals of groups 4, 5 and 6 of
the periodic table covers the circumferential surface of a
fiber-like core member 8b made of cBN sintered material constituted
from cBN particles that are bound by binder phase made of nitride 6
of at least one kind of metal element selected from among metals of
groups 4, 5 and 6 of the periodic table.
[0124] Even when the cBN sintered material has the single-filament
fiber-like structure described above, the cBN sintered material 10
as a whole has such a constitution that carbide 5 and nitride 6
coexist in the binder phase 3, and therefore similar effects to
those of the cBN sintered material 1 described previously can be
achieved. Moreover, when the cBN sintered material has the
single-filament fiber-like structure and one of the binder phases
of the core member and the shell member is made from carbide 5 and
the other from nitride 6, properties of the core member 8 and the
shell member 9 can be put into action in a well-balanced manner,
thus causing the cBN sintered material as a whole to exhibit the
best performance. As a result, wear resistance and chipping
resistance of the cBN sintered material are improved more
effectively. It is also made possible to preferentially improve
either wear resistance or chipping resistance by controlling the
direction of fiber.
[0125] The cBN sintered material of fiber-like structure may be,
besides the single-filament fiber-like structure described above, a
cBN sintered material 11 having multi-filament fiber-like structure
wherein a plurality of cBN sintered materials 10 having
single-filament fiber-like structure are bundled as shown in FIG.
5(a), 5(b). This constitution improves the wear resistance and
chipping resistance further.
[0126] When bundling the cBN sintered materials 10 having
single-filament fiber-like structure, only the first cBN sintered
materials 10a may be bundled, or only the second cBN sintered
materials 10b may be bundled, or the first cBN sintered material
10a and the second cBN sintered material 10b may be bundled
together, depending on the application.
[0127] Dimensions of the cBN sintered materials of fiber-like
structure 10, 11 are preferably such that mean diameter d.sub.C of
the core member 8 shown in FIG. 4(a) is in a range from 10 to 200
.mu.m and thickness d.sub.S of the shell member 9 is in a range
from 1 to 20 .mu.m, in order to improve the chipping resistance of
the cutting tool that would be made thereof. Mean diameter d.sub.C
of the core member 8 and thickness of the shell member 9 may be
determined by observing the cross section of the cBN sintered
material of fiber-like structure 10, 11 under a scanning electron
microscope (SEM) or a metallurgical microscope.
[0128] The multi-filament fiber-like structure may be, besides the
bundled form shown in FIGS. 5(a), 5(b), constituted as shown in
FIGS. 6(a) to 6(d). FIG. 6(a) shows a cBN sintered material 16A
wherein the cBN sintered materials of fiber-like structure 10 (or
11) are arranged in sheet configuration, FIG. 6(b) shows a cBN
sintered material 16B wherein a plurality of the sheet-like cBN
sintered materials 16A are stacked in the same direction, FIG. 6(c)
shows a cBN sintered material 16C wherein a plurality of the
sheet-like cBN sintered materials 16A are stacked in different
directions, and FIG. 6(d) shows a cBN sintered material 16D wherein
the cBN sintered materials of fiber-like structure 10 (or 11) are
arranged in the direction perpendicular to the sheet surface. Such
a constitution may also be employed as the cBN sintered materials
of fiber-like structure 10 (or 11) are arranged at random.
[0129] The second embodiment described previously is a case where
the cBN sintered material 1 of which binder phase 3 contains
carbide 5 and nitride 6 coexisting therein shows the diffraction
peak of the nitride 6 and the diffraction peak of the carbide 5 at
the same time in the X-ray diffraction analysis. However the
present invention is not limited to such a case, and the cBN
sintered material of single-filament fiber-like structure 10, 11
may also show the diffraction peak of the nitride 6 and the
diffraction peak of the carbide 5 at the same time in the X-ray
diffraction analysis.
[0130] In case a cBN sintered material for cutting tool 30 to be
described later is made of the cBN sintered material of the second
embodiment, in particular, the ratio (I.sub.C/I.sub.N) of the
intensity I.sub.C of a diffraction peak attributed to plane (200)
of carbide 5 to intensity I.sub.N of a diffraction peak attributed
to (200) plane of the nitride 6 is controlled within a range from
0.2 to 1.2, preferably from 0.3 to 0.9 as measured by X-ray
diffraction analysis of the cross section of the fiber structure of
the cBN sintered material of fiber-like structure 10, 11 described
above, too. This enables it to prevent the cBN particles 2 from
coming off and prevent excessive wear from occurring, without
allowing the wear resistance to decrease during cutting operation.
It is preferable that the conditions described above are satisfied
also with regards to the ratio I.sub.N/I.sub.cBN, ratio
I.sub.C/I.sub.cBN, peak intensity I.sub.CN, peak intensity I.sub.C
and peak intensity I.sub.N of the second embodiment.
[0131] The third embodiment dealt with a case where the ratio
(d.sub.N/d.sub.C) has a predetermined value in the cBN sintered
material 1 wherein the binder phase 3 contains carbide 5 and
nitride 6 coexisting therein. However, the present invention is not
limited to this constitution, and it is preferable that the ratio
(d.sub.N/d.sub.C) has a predetermined value also in the cBN
sintered material 10, 11 having single-filament fiber-like
structure.
[0132] In case the cBN sintered material for cutting tool 30 to be
described later is made of the cBN sintered material of the third
embodiment, the cBN sintered material of fiber-like structure also
has the binder phase 3 that contains nitride 6 and carbide 5
coexisting therein when the cBN sintered material is considered as
a whole, and the nitride 6 and the carbide 5 are characterized in
that the ratio (d.sub.N/d.sub.C) of mean grain size d.sub.N of the
nitride 6 to mean grain size d.sub.C of the carbide 5 is in a range
from 0.4 to 1.2. It is also preferable that mean particle size
d.sub.cBN of the cBN particles 2 is 5 .mu.m or smaller, mean grain
size d.sub.C of the carbide 5 is from 1 to 3 .mu.m and mean grain
size d.sub.N of the nitride 6 is from 0.5 to 2 .mu.m. This enables
it to prevent the cBN particles 2 from coming off, which is
impossible with the conventional binder phase. As a result, it is
made possible to prevent the cBN particles from coming off and the
binder phase from wearing and coming off at the same time, thus
providing the cBN sintered material having high wear resistance
and, especially, excellent chipping resistance.
[0133] In the cBN sintered material of fiber-like structure 10, 11,
too, it is preferable that 300 MPa or higher residual compressive
stress .sigma..sub.cBN remains in the cBN particles 2. This enables
it to suppress the cBN particles 2 from coming off. In the case of
the cBN sintered material of fiber-like structure 10, 11, both the
residual compressive stress .sigma..sub.cBN of the cBN particles 2
and residual compressive stress .sigma..sub.b of the binder phase 3
tend to be higher than in the case of the conventional uniform
ceramic structure described previously.
[0134] The fifth embodiment dealt with a case where the cBN
sintered material 1 wherein the binder phase 3 contains carbide 5
and nitride 6 coexisting therein is covered by the hard film 40 on
the surface thereof. However, the present invention is not limited
to this constitution, and the hard film 40 may also cover the
surface of the shell member 9 of the cBN sintered material 10, 11
having the single-filament and multi-filament fiber-like
structure.
[0135] An example of method for manufacturing the cBN sintered
material of fiber-like structure, that is another cBN sintered
material of this embodiment will now be described in detail with
reference to the accompanying drawing. FIGS. 7(a) and 7(b) are
schematic diagrams showing a method of manufacturing a composite
green compact made of the cBN sintered material having
single-filament fiber-like structure.
[0136] First, a stock material for core member is prepared by
crushing and mixing the materials similarly to the process of the
method of manufacturing the cBN sintered material described above,
except for adding only one of the carbide and nitride as the binder
phase component. Then an organic binder is added to the stock
material for core member and mixed. The mixture is formed in a
cylindrical shape by press molding, extrusion molding, casting or
the like, thereby to make a green compact of core member 17 shown
in FIG. 7(a).
[0137] For the organic binder, for example, paraffin wax,
polystyrene, polyethylene, ethylene-ethyl acryl ate, ethylene-vinyl
acetate, polybutyl-methacrylate, polyethylene glycol or
dibutylphthalate may be used.
[0138] Then a stock material for shell member is prepared similarly
to the process of the method described above, except for adding one
of the carbide and nitride, one other than that used in the stock
material for core member as the binder phase component. Then the
binder described above is added to the stock material for shell
member and mixed. Two green compact of shell members 18 having
semi-cylindrical shape shown in FIG. 7(a) are formed from the
mixture by the forming method described above. The green compact of
shell member 18 are disposed around the green compact of core
member 17 so as to surround the circumference thereof, thereby to
make the composite green compact 19.
[0139] Then the composite green compact 19 is formed by
simultaneous extrusion (co-extrusion) molding as shown in FIG.
7(b). That is, the green compact of core member 17 and the green
compact of shell member 18 are extrusion molded at the same time.
This process makes a composite green compact 20 having the
single-filament fiber-like structure extended with a small
diameter, wherein the green compact of shell members 18 are
disposed on the green compact of core member 17 so as to cover the
circumference thereof.
[0140] The green compact 21 having multi-filament fiber-like
structure may be formed by bundling a plurality of composite green
compacts 20 of single-filament fiber-like structure that have been
subjected to the simultaneous extrusion molding, and applying
simultaneous extrusion molding again to the bundle. With this
method, it is made possible to further increase the bonding
strength between the composite materials in the green compact
20.
[0141] In the simultaneous extrusion molding process, cross section
of the fiber-like green compacts that are extended as described
above can be made in a desired shape including circle, triangle,
rectangle and hexagon, by changing the extrusion die.
[0142] In order to form the composite structure constituted from
the composite materials shown in FIG. 6 arranged in a sheet-like
configuration, the composite green compacts 20 made as described
above are arranged to form the sheet-like green compact 22. The
composite green compacts 20 in the sheet-like green compact 22 may
be stacked in parallel to each other, or in such a manner as to
cross each other at an angle of 90.degree. or 45.degree.. In this
case, the sheet-like green compact 22 may also be pressurized by
cold isostatic pressing (CIP) or the like, with a bonding material
such as the adhesion described above between the composite green
compacts 20, as required. Alternatively, the sheet-like green
compact 22 may also be formed by rolling by means of a pair of
rolls 23 as shown in FIG. 9. The sheet-like green compact 22 may
also be made by employing a forming method such as the known rapid
prototyping method when disposing the composite materials (cBN
sintered materials 16A to 16D shown in FIG. 6). The green compact
21 may also be used instead of the composite green compact 20.
[0143] Then the green compacts 20 to 22 made as described above are
heated at a temperature from 600 to 1000.degree. C. for a period of
1 to 72 hours in vacuum of 2 Pa or lower pressure, to carry out
degreasing heat treatment. The green compact thus treated is
charged, together with a backing member made of cemented carbide
prepared separately, in an ultra-high pressure firing apparatus,
and is fired under the conditions described previously so as to
obtain the cBN sintered material of fiber-like structure.
[0144] The firing may also be carried out by charging the green
compact thus degreased, together with the backing member made of
cemented carbide prepared separately, in the ultra-high pressure
sintering apparatus, and sintering it in the state of being bonded
with the backing member made of cemented carbide in an integral
body. The sintered body is ground or polished to a predetermined
thickness by means of diamond wheel, electrolytic polishing,
brushing or the like.
[0145] When a cutting tool is made of the cBN sintered material, a
cutting edge of high strength and sharper cutting may be formed by
applying C face treatment or R face treatment to the edge of the
sintered material by means of an elastic grinding stone, brush or
the like.
<Cutting Tool>
[0146] A cutting tool according to the present invention will now
be described, that is provided with the cBN sintered material of
the embodiments described above, with reference to the accompanying
drawings. FIG. 10 is a perspective view showing an embodiment of
the cutting tool according to the present invention. As shown in
FIG. 10, the tool tip 12 has such a structure as a cBN sintered
material for cutting tool 30 cut into a predetermined shape is
brazed via a backing member 15 onto a tip mounting seat provided at
a corner of a tool insert 13. The cBN sintered material for cutting
tool 30 has cutting edges 14 formed along the edges where the top
surface and the side faces meet.
[0147] FIG. 11 is a schematic sectional view showing the
constitution of the corner of the tool tip 12 that employs the cBN
sintered material of fiber-like structure described above. FIG.
11(a) is a schematic sectional view showing an example and FIG.
11(b) is a schematic sectional view showing another example. In the
tool tip 12 shown in FIG. 11(a), the cBN sintered material for
cutting tool 30 is constituted from a sheet-like cBN sintered
material 16C, where the cBN sintered material of fiber-like
structure 10 (or 11) is disposed so that the direction of fibers
are disposed in parallel to the rake face 31 (cross sections of the
fibers are exposed on the flank 32).
[0148] In the tool tip 12 shown in FIG. 11(b), the cBN sintered
material for cutting tool 30 is constituted from a cBN sintered
material 16D, where the cBN sintered material of fiber-like
structure 10 (or 11) is disposed so that the direction of fibers
are disposed in parallel to the flank 32 (cross sections of the
fibers are exposed on the rake face 31).
[0149] In addition to the constitution described above, such
constitutions as the fiber of the cBN sintered material of
fiber-like structure 10 (or 11) is directed at a predetermined
angle from the rake face 31, or the fibers of the cBN sintered
material of fiber-like structure 10 (or 11) are disposed in random
directions. Among these constitutions, the constitution shown in
FIG. 11(b) is desirable in order to improve chipping resistance.
The tool tip 12 may be made by advantageously using the simple cBN
sintered material 1 described above, besides the cBN sintered
material of fiber-like structure 10 (or 11).
[0150] The cBN sintered material exhibits excellent wear resistance
and chipping resistance, and can be preferably used as a structural
material that is required to have wear resistance and chipping
resistance such as drill bits of excavating tool and anti-wear
material for die or sliding member. The cBN sintered material can
be used for a cutting tool with a long service life, to exhibit
excellent performance in metal cutting operations with a cutting
edge, that is formed along a ridge where a flank and a rake face
thereof meet, being pressed against a workpiece to be cut,
particularly a metal such as iron or aluminum, or heat resistance
alloy. The cBN sintered material exhibits excellent cutting
performance in machining of hard-to-cut metals such as hardened
steel.
[0151] When used in a cutting tool, the cutting tool preferably has
such a constitution that comprises a tool insert and a tool tip
brazed at the mounting seat of the tool insert, where the tool tip
is made of the cBN sintered material of this embodiment. In this
case, while the residual stress remaining in the cBN sintered
material tends to be temporarily released when brazing the tool
tip, the residual stress remaining in the cBN sintered material of
the tool tip is controlled within a proper range so as to achieve
high wear resistance and high chipping resistance.
[0152] The present invention will be described in detail by way of
examples, but it is understood that the present invention is not
limited by the following examples.
EXAMPLE I
[0153] A cBN material powder having a mean particle size of 2
.mu.m, TiC material powder having a mean particle size of 1 .mu.m,
TiN material powder having a mean particle size of 1 .mu.m, TiCN
material powder having a mean particle size of 1 .mu.m, HfC
material powder having a mean particle size of 1 .mu.m, NbC
material powder having a mean particle size of 1 .mu.m, metal Al
powder having a mean particle size of 1.2 .mu.m and metal Co powder
having a mean particle size of 0.8 .mu.m were prepared in
proportions shown in Table 1, and were mixed in a ball mill using
alumina balls for 16 hours.
[0154] Then the mixed powder was press formed under a pressure of
98 MPa. This green compact was fired under the conditions shown in
Table 1 in an ultra-high pressure, high temperature apparatus,
namely heated at the temperature raising rate shown in Table 1,
held under pressure of 5.0 GPa at the firing temperature shown in
Table 1 for the period therein, and then cooled down at the
temperature lowering rate shown in Table 1, thereby to obtain the
cBN sintered material (samples Nos. I-1 to I-10 shown in Table
1).
(Content)
[0155] The samples of the cBN sintered material obtained in the
process described above were ground and polished to mirror finish,
and the structures thereof were observed under a metallurgical
microscope. The cBN particles appearing in black, nitride appearing
in brown and carbide appearing in white were clearly distinguished,
while the intermediate phase and the carbonitride were also
distinguished through EPMA (electron probe microanalysis) using a
WDS (wavelength-dispersion type X-ray spectrometer). Areas of 20 or
more grains of each compound were measured by image analysis, and
mean values of the areas were taken to represent the contents of
the cBN particles, carbide, nitride, the intermediate phase and the
carbonitride. The results are shown in Table 1. Presence of
carbonitride was determined by observing the peak in X-ray
diffraction analysis. When the corresponding peak was observed,
proportion of the content of that component was determined by
comparing with the standard sample (green compact made of a mixture
of cBN particles and carbonitride powder). TABLE-US-00001 TABLE 1
Firing condition Temperature Firing Firing Temperature Sample
Proportion (% by volume) raising rate temperature period lowering
rate No..sup.1) cBN Carbide Nitride Metal Others (.degree. C./min.)
(.degree. C.) (minute) (.degree. C./min.) .sup. I-1 the rest TiC:
15 TiN: 25 Al: 10 -- 50 1400 15 50 .sup. I-2 the rest TiC: 10 TiN:
15 Al: 5 -- 50 1400 15 50 WC: 5 Co: 3 .sup. I-3 the rest HfC: 20
TiN: 10 Al: 10 -- 50 1400 15 50 .sup. I-4 the rest TiC: 3 TiN: 8
Al: 10 -- 50 1400 15 50 Co: 5 * I-5 the rest TiC: 45 -- Al: 15 --
50 1400 15 50 * I-6 the rest -- TiN: 35 Al: 15 -- 50 1400 15 50 *
I-7 the rest -- -- Al: 8 TiCN: 37 50 1400 15 50 * I-8 the rest TiC:
21 TiN: 3 Al: 3 -- 50 1400 15 50 NbC: 10 Co: 3 * I-9 the rest TiC:
25 TiN: 15 Al: 15 -- 50 1500 15 50 * I-10 the rest TiC: 15 TiN: 15
Al: 10 -- 20 1400 30 20 Content proportion in sintered
material.sup.2) Sample Intermediate No..sup.1) cBN Carbide Nitride
phase Carbonitride p.sub.C/p.sub.N .sup. I-1 47 13 22 16 2 0.6
.sup. I-2 58 15 13 13 1 1.2 .sup. I-3 56 16 7 21 -- 2.3 .sup. I-4
78 3 7 12 -- 0.4 * I-5 42 43 -- 15 -- -- * I-6 50 -- 32 18 -- -- *
I-7 54 -- -- 11 35 -- * I-8 58 30 -- 4 8 -- * I-9 53 8 -- 10 27 --
* I-10 67 -- -- 8 25 -- .sup.1)Samples marked `*` are out of the
scope of the present invention. .sup.2)Content proportion: cBN
particles, carbide and nitride were observed under a metallurgical
microscope (% by area), The content of carbonitride was calculated
from XRD peak.
[0156] The samples of the cBN sintered material were cut to
predetermined dimensions by wire discharge cutting or the like,
each being brazed onto a mounting seat of a cemented carbide
substrate, thereby to make throwaway cutting tool having the
configuration specified in JIS CNGA120408, that was subjected to
continuous cutting test and interrupted cutting test under the
following conditions. The results are shown in Table 2.
(Continuous Cutting Test)
[0157] Mode of cutting: Turning [0158] Workpiece: SCM415H
carburizing-hardened steel (HRC58-62) having cylindrical shape 70
mm in diameter [0159] Cutting speed: 200 m/min. [0160] Infeed: 0.2
mm [0161] Feed rate: 0.1 mm/rev. [0162] Cutting time: 20 minutes
[0163] Measurement: Amount of wear at the distal end (Interrupted
Cutting Test) [0164] Mode of cutting: Turning [0165] Workpiece:
SCM415H carburizing-hardened steel (HRC58-62) having lotus root
shape with 8 holes [0166] Cutting speed: 150 m/min. [0167] Infeed:
0.2 mm [0168] Feed rate: 0.2 mm/rev.
[0169] Measurement: Number of impacts before chipping (Upper limit
40000) TABLE-US-00002 TABLE 2 Sample Continuous cutting test
Interrupted cutting test No..sup.1) Amount of wear(mm) Number of
impacts I-1 0.12 40000 I-2 0.14 36000 I-3 0.18 35000 I-4 0.16 32000
*I-5 0.25 10000 *I-6 0.24 16000 *I-7 0.20 13000 *I-8 0.16 8000 *I-9
0.18 13500 *I-10 0.19 12000 .sup.1)Samples marked `*` are out of
the scope of the present invention.
[0170] The results shown in Tables 1 and 2 show that samples Nos.
I-5, 8 and 9 that contained only carbide (TiC) in the sintered
material had unsatisfactory chipping resistance because of
insufficient bonding between the cBN particles. Sample No. I-6 that
contained only nitride (TiN) in the sintered material had
unsatisfactory wear resistance, and performed with short service
life. Samples Nos. I-7 and 10 where the binder phase was
constituted from only carbonitride (TiCN) showed unsatisfactory
performance in wear resistance and in chipping resistance.
[0171] Cutting tools made of the cBN sintered material (samples
Nos. I-1 to 4) of the present invention, in contrast, all exhibited
sufficient wear resistance with amount of wear 0.20 mm or less in
continuous machining of carburizing-hardened steel that is hard to
cut. In interrupted machining, these samples endured 30000 or more
impacts before chipping. Samples Nos. I-1 and 4, in particular,
showed excellent chipping resistance with no chipping after 40000
impacts, and demonstrated stable cutting performance over an
extended period of time.
EXAMPLE II
[0172] The green compact of core member was made by extrusion
molding of a material that was prepared by mixing 45% by volume of
cBN, 42% by volume of TiN and 15% by volume of Al and adding an
organic binder thereto. The green compact of skin member was made
by extrusion molding of a material that was prepared by mixing 55%
by volume of cBN, 35% by volume of TiC and 10% by volume of Al and
adding an organic binder thereto.
[0173] The green compact of core member and the green compact of
shell member made as described above were extrusion molded as shown
in FIG. 7, thereby to make a composite green compact. The composite
green compacts were bundled together to make a composite green
compact of multi-filament structure in a manner shown in FIG. 8.
The composite green compacts of multi-filament structure were
further arranged in sheet configuration, and the sheets were
stacked and pressed. The stack was fired by raising the temperature
at a rate of 50.degree. C. per minute, holding it under pressure of
5.0 GPa at a temperature of 1400.degree. C. for 15 minutes, then
lowering the temperature at a rate of 50.degree. C. per minute in
an ultra-high pressure, high temperature apparatus, thereby to
obtain the composite cBN sintered material.
[0174] The samples of the composite cBN sintered material obtained
in the process described above were ground and polished to mirror
finish, and the structures thereof were observed under a
metallurgical microscope. The cBN particles appearing in black,
nitride (TiN) appearing in brown and carbide (TiC) appearing in
white were clearly distinguished, while carbonitride (TiCN) could
also be distinguished. Proportions of the areas occupied by various
components measured by image analysis were 50% for cBN, 10% for
TiC, 25% for TiN and 2% for TiCN.
[0175] The samples of the cBN sintered material were cut to
predetermined dimensions by wire discharge cutting, each being
brazed onto a mounting seat of a cemented carbide substrate,
thereby to make a throwaway cutting tool having the configuration
specified in JIS CNGA120408, that was subjected to cutting tests
similarly to Example I. The samples experienced the amount of wear
as small as 0.15 mm after cutting for 20 minutes, showed no
chipping after being subjected to 40000 impacts in interrupted
machining test, thus exhibiting excellent cutting performance.
EXAMPLE III
[0176] cBN material powder having a mean particle size of 2 .mu.m,
TiC material powder having a mean particle size of 1 .mu.m, TiN
material powder having a mean particle size of 1 .mu.m, TiCN
material powder having a mean particle size of 1 .mu.m, HfC
material powder having a mean particle size of 1 .mu.m, TaC
material powder having a mean particle size of 1 .mu.m, metal Al
powder having a mean particle size of 1.2 .mu.m and metal Co powder
having a mean particle size of 0.8 .mu.m were prepared in
proportions shown in Table 3, and were mixed in a ball mill using
alumina balls for 16 hours, and the mixed powder was press formed
under a pressure of 98 MPa.
[0177] This green compact was fired similarly to Example I except
for employing the firing conditions shown in Table 3, instead of
the conditions shown in Table 1 in an ultra-high pressure, high
temperature apparatus, thereby to obtain the cBN sintered material
(samples Nos. III-1 to 10 shown in Table 3). TABLE-US-00003 TABLE 3
Firing condition Temperature Firing Firing Temperature Sample
Proportion (% by volume) raising rate temperature period lowering
rate No..sup.1) cBN Carbide Nitride Metal Others (.degree. C./min.)
(.degree. C.) (minute) (.degree. C./min.) .sup. III-1 the rest TiC:
20 TiN: 30 Al: 10 -- 50 1400 15 50 .sup. III-2 the rest TiC: 13
TiN: 16 Al: 5 -- 30 1300 30 45 WC: 5 Co: 3 .sup. III-3 the rest
HfC: 20 TiN: 15 Al: 10 -- 40 1400 20 30 .sup. III-4 the rest TaC: 3
TiN: 14 Al: 10 -- 50 1250 25 50 Ni: 5 * III-5 the rest TiC: 40 --
Al: 15 -- 50 1400 10 100 * III-6 the rest -- TiN: 40 Al: 15 -- 50
1400 10 100 * III-7 the rest -- -- Al: 8 TiCN: 37 50 1400 10 100 *
III-8 the rest TiC: 15 TiN: 15 Al: 15 -- 50 1500 15 50 * III-9 the
rest TiC: 20 TiN: 10 Al: 15 -- 50 1400 30 20 * III-10 the rest TiC:
10 TiN: 25 Al: 8 -- 100 1600 10 100 .sup.1)Samples marked `*` are
out of the scope of the present invention.
(Intensities of X-ray Diffraction Peaks)
[0178] The samples of cBN sintered material were subjected to X-ray
diffraction analysis (XRD) at angle of 2.theta.=30 to 50.degree.
using Cu-K.alpha. line source (with K.sub..alpha.2 line removed),
peaks of carbide and nitride were identified in the diffraction
chart, and the intensity ratio of the carbide and nitride peaks was
calculated. The results are shown in Table 4.
(Cutting Test)
[0179] The samples of the cBN sintered material were used to make
throwaway cutting tool having the configuration specified in JIS
CNGA120408, similarly to Example I. Continuous cutting test and
interrupted cutting test were conducted similarly to Example I,
except for setting the limit for the number of impacts experienced
before chipping in the interrupted cutting test to 60000 instead of
40000. The results are shown in Table 4. TABLE-US-00004 TABLE 4
Continuous Interrupted Intensity of XRD analysis peak.sup.2)
cutting test cutting test Sample cBN Nitride Carbide Carbonitride
Intermediate Amount of wear Number of No..sup.1) I.sub.cBN I.sub.N
I.sub.C I.sub.CN I.sub.C/I.sub.N I.sub.N/I.sub.cBN
I.sub.C/I.sub.cBN phase (mm) impacts .sup. III-1 100 85 35 2 0.41
0.85 0.35 TiB.sub.2, AlN 0.13 45000 .sup. III-2 100 62 50 12 0.81
0.62 0.50 TiB.sub.2, WCoB 0.14 39000 .sup. III-3 100 57 60 -- 1.05
0.57 0.60 No exist 0.18 38000 .sup. III-4 100 88 20 -- 0.23 0.88
0.20 AlN 0.16 33000 * III-5 100 -- 68 -- -- -- 0.68 TiB.sub.2, AlN
0.25 12000 * III-6 100 70 -- -- -- 0.70 -- No exist 0.24 16000 *
III-7 100 -- -- 52 -- -- -- No exist 0.20 14000 * III-8 100 -- --
45 -- -- -- AlN, TiB.sub.2 0.21 12000 * III-9 100 2 -- 40 -- 0.02
-- AlN 0.20 8000 * III-10 100 -- 5 35 -- -- 0.05 AlN, TiB.sub.2
0.26 15000 .sup.1)Samples marked `*` are out of the scope of the
present invention. .sup.2)The mark `--` in the columns of cBN,
Nitride, Carbide and Carbonitride indicates that the peak was not
detected.
[0180] The results shown in Tables 3 and 4 indicate that sample No.
III-5, from which only the peak of carbide was observed, was
insufficient in chipping resistance because of insufficient bonding
between the cBN particles. Sample No. III-6, from which only the
peak of nitride was observed, was insufficient in wear resistance
which resulted in a short tool life. Sample No. III-7 made by using
TiCN powder for the binder phase and sample No. III-8 where the
binder phase turned into TiCN phase by firing were insufficient in
both wear resistance and chipping resistance. Sample No. III-9
where the binder phase consisted of TiCN phase and TiC phase and
sample No. III-10 where the binder phase consisted of TiCN phase
and TiN phase were insufficient in both wear resistance and
chipping resistance.
[0181] Samples Nos. III-1 to 4 that were tool tips made of sintered
material that shows XRD peak of TiC and XRD peak of TiN exhibited
sufficient wear resistance with the amount of wear not larger than
0.20 mm in continuous cutting of carburizing-hardened steel, that
is a hard-to-cut material. These tool tips exhibited excellent
chipping resistance, in particular, in the interrupted cutting test
by enduring 30000 impacts or more before chipping and demonstrated
stable cutting performance over an extended period of time.
EXAMPLE IV
[0182] The green compact of core member was made similarly to
Example II. Then green compact of shell member was made similarly
to Example II, except for changing the content of TiC from 35% by
volume to 30% by volume. The green compact of core member and the
green compact of shell member were used to make the composite green
compact of multi-filament structure similarly to Example II, which
was fired to make composite cBN sintered material.
[0183] X-ray diffraction analysis (XRD) was conducted on the cross
section of the composite cBN sintered material, and the peak of
carbide in the shell member and the peak of nitride in the core
member were identified in the diffraction chart. The ratio
(I.sub.C/I.sub.N) of the intensity I.sub.C of peak of carbide to
intensity I.sub.N of peak of nitride was 0.42. Microscopic
observation and composition analysis showed the presence of TiN in
the core member and TiC in the shell member.
[0184] The sintered material was cut to predetermined dimensions by
wire discharge cutting, each being brazed onto a mounting seat of a
cemented carbide substrate, thereby to make a throwaway cutting
tool having the configuration specified in JIS CNGA120408, that was
subjected to cutting tests similarly to Example I. The samples
experienced the amount of wear as small as 0.15 mm after cutting
for 20 minutes, showed no chipping after being subjected to 60000
impacts in interrupted machining test, thus exhibiting excellent
cutting performance.
EXAMPLE V
[0185] cBN material powder having a mean particle size of 2.5
.mu.m, TiC material powder having a mean particle size of 1.5
.mu.m, TiN material powder having a mean particle size of 1.2
.mu.m, TiCN material powder having a mean particle size of 1 .mu.m,
NbC material powder having a mean particle size of 1 .mu.m, TaC
material powder having a mean particle size of 1.1 .mu.m, NbN
material powder having a mean particle size of 0.9 .mu.m, metal Al
powder having a mean particle size of 1.2 .mu.m and metal Co powder
having a mean particle size of 0.8 .mu.m were prepared in
proportions shown in Table 5, and were mixed in a ball mill using
alumina balls for 16 hours.
[0186] The mixed powder was press formed under a pressure of 98
MPa. This green compact was fired similarly to Example I except for
employing the firing conditions shown in Table 5, instead of the
conditions shown in Table 1 in an ultra-high pressure, high
temperature apparatus, thereby to obtain the cBN sintered material
(samples Nos. V-1 to 10 shown in Table 5). TABLE-US-00005 TABLE 5
Firing condition Temperature Firing Firing Temperature Sample
Proportion (% by volume) raising rate temperature period lowering
rate No..sup.1) cBN Carbide Nitride Metal Others (.degree. C./min.)
(.degree. C.) (minute) (.degree. C./min.) Remarks .sup. V-1 the
rest TiC: 25 TiN: 25 Al: 12 -- 50 1400 15 50 Brazed tip .sup. V-2
the rest TiC: 12 TiN: 15 Al: 6 -- 30 1300 30 45 Brazed tip WC: 8
Co: 4 .sup. V-3 the rest NbC: 15 NbN: 20 Al: 10 -- 40 1400 20 30
Brazed tip .sup. V-4 the rest TaC: 10 TiN: 12 Al: 15 -- 50 1250 25
50 Brazed tip Ni: 3 * V-5 the rest TiC: 36 -- Al: 14 -- 50 1400 10
100 Brazed tip * V-6 the rest -- TiN: 40 Al: 10 -- 50 1400 10 100
Brazed tip * V-7 the rest -- -- Al: 7 TiCN: 28 50 1400 10 100
Brazed tip * V-8 the rest TiC: 15 TiN: 15 Al: 10 -- 50 1500 15 50
Brazed tip * V-9 the rest TiC: 20 TiN: 10 Al: 15 -- 50 1400 30 20
Brazed tip * V-10 the rest TiC: 10 TiN: 20 Al: 8 -- 100 1600 10 100
Brazed tip .sup.1)Samples marked `*` are out of the scope of the
present invention.
(Intensities of X-ray Diffraction Peaks)
[0187] The samples were subjected to X-ray diffraction analysis
(XRD), and peaks of carbide, nitride and other components were
identified in the diffraction chart, similarly to Example III. The
intensity ratio of the peaks shown in Table 6 was calculated.
(Mean Particle Size)
[0188] Microstructure was observed in colors by means of a
metallurgical microscope, and the states of nitride and carbide
existing in the binder phase were checked. Mean particle sizes
d.sub.N, d.sub.C, d.sub.cBN were measured by means of Luzex image
analyzer. Values of d.sub.N, d.sub.C, d.sub.cBN were determined by
using 50 or more grains for each phase shown in the
microsctructural photograph.
[0189] In case less than 50 grains of a phase could be seen within
a single field of view, grains of the phase shown in other field of
view were observed and taken into account. A set of measurements
for 50 or more grains of each phase was carried out at each of
three or more points, with mean values thereof being taken as
d.sub.N, d.sub.C, d.sub.cBN.
Results of the measurements are summarized in Table 6.
(Cutting Test)
[0190] The samples of the cBN sintered material were used to make
throwaway cutting tool having the configuration specified in JIS
CNGA120408, similarly to Example I. Then continuous cutting test
and interrupted cutting test were conducted similarly to Example I,
except for setting the limit for the number of impacts experienced
before chipping in the interrupted cutting test to 60000 instead of
40000. The results are shown in Table 6. TABLE-US-00006 TABLE 6
Continuous cutting test Interrupted Intensity of XRD analysis peak
Inter- Amount cutting test Sample d.sub.cBN dc d.sub.N cBN Nitride
Carbide Carbonitride mediate of wear Number of No..sup.1) (.mu.m)
(.mu.m) (.mu.m) d.sub.N/d.sub.c I.sub.cBN I.sub.N I.sub.C I.sub.CN
I.sub.C/I.sub.N I.sub.N/I.sub.cBN I.sub.C/I.sub.cBN phase (mm)
impacts .sup. V-1 2.2 1.2 0.7 0.6 100 70 40 2 0.57 0.70 0.40
TiB.sub.2, AlN 0.15 43200 .sup. V-2 0.8 1.0 0.4 0.4 100 60 45 12
0.75 0.60 0.45 TiB.sub.2, WCoB 0.14 38400 .sup. V-3 2.8 1.5 1.8 1.2
100 40 28 -- 0.70 0.40 0.28 No exist 0.18 31200 .sup. V-4 3.8 3.2
2.4 0.8 100 64 20 -- 0.31 0.64 0.20 AlN 0.20 36400 * V-5 3.8 2.4 --
-- 100 -- 68 -- -- -- 0.68 TiB.sub.2, AlN 0.24 11600 * V-6 1.2 --
0.8 -- 100 70 -- -- -- 0.70 -- No exist 0.28 18000 * V-7 1.8 -- --
-- 100 -- -- 52 -- -- -- No exist 0.20 14000 * V-8 2.0 -- -- -- 100
-- -- 45 -- -- -- AlN, TiB.sub.2 0.21 12000 * V-9 2.0 1.5 -- -- 100
2 -- 40 -- 0.02 -- AlN 0.20 8800 * V-10 2.0 -- 2.0 -- 100 -- 5 35
-- -- 0.05 AlN, TiB.sub.2 0.26 15600 .sup.1)Samples marked `*` are
out of the scope of the present invention.
[0191] The results shown in Tables 5 and 6 indicate that samples
Nos. V-5 to 10, wherein the binder phase does not have coexistence
of carbide and nitride, all had weak binding between the cBN
particles, and were therefore insufficient in chipping resistance
which resulted in a short tool life.
[0192] Samples Nos. V-1 to 4, wherein the binder phase contains
nitride and carbide coexisting therein, and the ratio
d.sub.N/d.sub.C of mean grain size d.sub.N of the nitride to mean
grain size d.sub.C of the carbide is in a range from 0.4 to 1.2, in
contrast, all showed sufficient wear resistance with the amount of
wear not larger than 0.20 mm in continuous cutting of
carburizing-hardened steel, that is a hard-to-cut material, and
exhibited excellent chipping resistance, in particular, with 30000
impacts or more before chipping in the interrupted cutting test and
demonstrated stable cutting performance over an extended period of
time.
EXAMPLE VI
[0193] The green compact of core member was made by extrusion
molding of a powder material that was prepared by mixing 47% by
volume of cBN, 39% by volume of TiN and 14% by volume of Al and
adding an organic binder thereto. The green compact of shell member
was made by extrusion molding of a material that was prepared by
mixing 60% by volume of cBN, 30% by volume of TiC and 10% by volume
of Al and adding an organic binder thereto.
[0194] The green compact of core member and the green compact of
shell member made as described above were used to form composite
green compact of multi-filament structure similarly to Example II
and were fired thereby to make a composite cBN sintered
material.
[0195] Image analysis of nitride (TiN) and carbide (TiC) in the cBN
sintered material by microscopic observation showed mean grain size
d.sub.C=1.2 .mu.m for the carbide, mean grain size d.sub.N=0.7
.mu.m for the nitride and the ratio d.sub.N/d.sub.C=0.6. X-ray
diffraction analysis (XRD) conducted on the core member and the
shell member made of the cBN sintered material showed the presence
of peak of carbide and peak of nitride in the X-ray diffraction
chart, and the ratio I.sub.C/I.sub.N of peak intensity I.sub.C of
the carbide to peak intensity I.sub.N of nitride was determined to
be 0.42.
[0196] The sintered material was cut to predetermined dimensions by
wire discharge cutting, each being brazed onto a mounting seat of a
cemented carbide substrate, thereby to make a throwaway cutting
tool having the configuration specified in JIS CNGA120408, that was
subjected to cutting tests similarly to Example I. The samples
experienced the amount of wear as small as 0.16 mm after cutting
for 20 minutes, showed no chipping after being subjected to 60000
impacts in interrupted cutting test, thus exhibiting excellent
cutting performance.
EXAMPLE VII
[0197] cBN material powder having a mean particle size of 2 .mu.m,
TiC material powder having a mean particle size of 1 .mu.m, TiN
material powder having a mean particle size of 1 .mu.m, TiCN
material powder having a mean particle size of 1 .mu.m, TaC
material powder having a mean particle size of 1 .mu.m, ZrC
material powder having a mean particle size of 1.2 .mu.m, ZrN
material powder having a mean particle size of 1.1 .mu.m, WC
material powder having a mean particle size of 0.9 .mu.m, metal Al
powder having a mean particle size of 1.2 .mu.m and metal Co powder
having a mean particle size of 0.8 .mu.m were prepared in
proportions shown in Table 7, and were mixed in a ball mill using
alumina balls for 16 hours.
[0198] The mixed powder was press formed under a pressure of 98
MPa. This green compact was fired similarly to Example I except for
employing the firing conditions shown in Table 7, instead of the
conditions shown in Table 1 in an ultra-high pressure, high
temperature apparatus, thereby to obtain the cBN sintered material
(samples Nos. VII-1 to 12 shown in Table 7).
[0199] The samples of the cBN sintered material were used to make
throwaway cutting tool having the configuration specified in JIS
CNGA120408, similarly to Example I. Sample No. VII-11 was formed
into a tool tip individually without brazing a piece of sintered
material cut by wire discharge. Sample No. VII-12 was coated with
TiAlN layer formed to a thickness of 1 .mu.m by ion plating method
at temperature of 500.degree. C. with bias voltage of 30 V.
TABLE-US-00007 TABLE 7 Firing condition Temperature Firing Firing
Temperature Sample Proportion (% by volume) raising rate
temperature period lowering rate No..sup.1) cBN Carbide Nitride
Metal Others (.degree. C./min.) (.degree. C.) (minute) (.degree.
C./min.) Remarks .sup. VII-1 the rest TiC: 20 TiN: 25 Al: 10 -- 50
1400 15 50 Brazed tip .sup. VII-2 the rest TiC: 10 TiN: 13 Al: 3 --
30 1350 30 45 Brazed tip WC: 7 Co: 4 .sup. VII-3 the rest ZrC: 15
ZrN: 20 Al: 10 -- 40 1400 20 30 Brazed tip .sup. VII-4 the rest
TaC: 5 TiN: 15 Al: 12 -- 50 1375 25 50 Brazed tip Co: 3 * VII-5 the
rest TiC: 35 -- Al: 15 -- 50 1400 10 100 Brazed tip * VII-6 the
rest -- TiN: 40 Al: 15 -- 50 1400 10 100 Brazed tip * VII-7 the
rest -- -- Al: 8 TiCN: 37 50 1400 10 100 Brazed tip * VII-8 the
rest TiC: 15 TiN: 15 Al: 15 -- 20 1500 15 50 Brazed tip * VII-9 the
rest TiC: 20 TiN: 10 Al: 15 -- 50 1400 30 20 Brazed tip * VII-10
the rest TiC: 10 TiN: 25 Al: 8 -- 100 1600 10 100 Brazed tip .sup.
VII-11 the rest TiC: 20 TiN: 25 Al: 10 -- 50 1400 15 50 Individual
tip .sup. VII-12 the rest TiC: 20 TiN: 25 Al: 10 -- 50 1400 15 50
TiAlN coating .sup.1)Samples marked `*` are out of the scope of the
present invention.
(Intensities of X-ray Diffraction Peaks)
[0200] The samples of cBN sintered material were subjected to X-ray
diffraction analysis (XRD) similarly to Example III, and peak of
carbide, peak of nitride and other peaks were identified. Peak
intensity ratio shown in Table 8 was also determined.
(Residual Stress)
[0201] Residual stresses acting on the cBN particles and on the
binder phase were calculated by X-ray residual stress measuring
method (2.theta.-sin.sup.2.phi.) using peaks observed at an angle
of 2.theta..gtoreq.100.degree. using Fe-K.alpha. line for cBN and
Cu-K.alpha. line for TiC and TiN of the binder phase, for example
the peak attributed to (311) plane of cBN and the peak attributed
to (422) plane of the binder phase. This calculation used modulus
of elasticity E of 712 GPa and Poisson ratio of 0.215 for the cBN
particles, modulus of elasticity E of 250 GPa and Poisson ratio of
0.19 for TiN and modulus of elasticity E of 400 GPa and Poisson
ratio of 0.19 for TiC.
[0202] Residual stresses of sample No. VII-11 was measured in a
sintered material that was cut out by wire discharging. Residual
stress of sample No. VII-12 was measured in a state of the TiAlN
layer being removed by electrolytic polishing.
(Cutting Test)
[0203] Continuous cutting test and interrupted cutting test were
conducted on the cBN sintered materials similarly to Example I,
except for setting the limit for the number of impacts experienced
before chipping in the interrupted cutting test to 60000 instead of
40000. The results are shown in Table 8. TABLE-US-00008 TABLE 8
Residual compressive stress Intensity of XRD analysis peak Sample
.sigma..sub.cBN .sigma..sub.C .sigma..sub.N .sigma..sub.b cBN
Carbide Nitride Carbonitride No..sup.1) (MPa) (MPa) (MPa)
.sigma..sub.c/.sigma..sub.N (MPa) .sigma..sub.cBN/.sigma..sub.b
I.sub.cBN I.sub.C I.sub.N I.sub.CN .sup. VII-1 600 340 220 1.5 250
2.4 100 35 80 2 .sup. VII-2 550 180 95 1.9 120 4.6 100 48 60 10
.sup. VII-3 450 285 80 3.6 175 2.6 100 55 42 -- .sup. VII-4 500 155
65 2.4 100 5.0 100 20 66 -- * VII-5 200 85 -- -- 85 2.4 100 68 --
-- * VII-6 110 -- 120 -- 120 0.9 100 -- 70 -- * VII-7 280 -- -- --
120 2.3 100 -- -- 52 * VII-8 95 -- -- -- 48 2.0 100 -- -- 45 *
VII-9 180 -- 100 -- 100 1.8 100 -- 2 40 * VII-10 130 25 -- -- 25
5.2 100 5 -- 35 .sup. VII-11 660 470 95 4.9 220 3.0 100 35 80 2
.sup. VII-12 530 234 130 1.8 185 2.9 100 35 80 2 Continuous
Interrupted cutting test cutting test Sample Intensity of XRD
analysis peak Intermediate Amount of Number of No..sup.1)
I.sub.C/I.sub.N I.sub.N/I.sub.cBN I.sub.C/I.sub.cBN phase wear(mm)
impacts .sup. VII-1 0.41 0.85 0.35 TiB.sub.2, AlN 0.14 45500 .sup.
VII-2 0.80 0.60 0.48 TiB.sub.2, WCoB 0.13 39000 .sup. VII-3 1.31
0.42 0.55 No exist 0.20 35500 .sup. VII-4 0.30 0.66 0.20 AlN 0.15
30500 * VII-5 -- -- 0.68 TiB.sub.2, AlN 0.25 12000 * VII-6 -- 0.70
-- No exist 0.28 16000 * VII-7 -- -- -- No exist 0.20 14000 * VII-8
-- -- -- AlN, TiB.sub.2 0.21 12000 * VII-9 -- 0.02 -- AlN 0.26
14000 * VII-10 -- -- 0.05 AlN, TiB.sub.2 0.18 8000 .sup. VII-11
0.44 0.80 0.35 TiB.sub.2, AlN 0.14 53500 .sup. VII-12 0.41 0.85
0.35 TiB.sub.2, AlN 0.09 40000 .sup.1)Samples marked `*` are out of
the scope of the present invention.
[0204] The results shown in Tables 7 and 8 indicate that samples
Nos. VII-5 to 10, wherein the residual compressive stress of the
cBN particles was less than 300 MPa had weak binding between the
cBN particles, and were therefore insufficient in chipping
resistance which resulted in a short service life.
[0205] Samples Nos. VII-1 to 4, 11 and 12, wherein the residual
compressive stress of the cBN particles was 300 MPa or higher, all
had sufficient wear resistance with the amount of wear not larger
than 0.20 mm in continuous cutting of carburizing-hardened steel,
that is a hard-to-cut material, and exhibited excellent chipping
resistance, in particular, with 30000 impacts or more before
chipping in the interrupted cutting test and demonstrated stable
cutting performance over an extended period of time.
EXAMPLE VIII
[0206] The green compact of core member was made by extrusion
molding of a powder material that was prepared by mixing 50% by
volume of cBN, 37% by volume of TiN and 13% by volume of Al and
adding an organic binder thereto. The green compact of shell member
was made by extrusion molding of a material that was prepared by
mixing 60% by volume of cBN, 30% by volume of TiC and 10% by volume
of Al and adding an organic binder thereto.
[0207] The green compact of core member and the green compact of
shell member made as described above were used to form composite
green compact of multi-filament structure similarly to Example II
and were fired thereby to make a composite cBN sintered
material.
[0208] Analysis of diffraction intensity obtained from X-ray
diffraction analysis (XRD) conducted on the core member and the
shell of the composite cBN sintered material showed residual
compressive stresses of .sigma..sub.cBN=717 MPa and
.sigma..sub.b=281 MPa. Peaks of carbide and nitride were observed,
and the ratio I.sub.C/I.sub.N of peak intensity I.sub.C of the
carbide to peak intensity I.sub.N of nitride was determined to be
0.42.
[0209] The sintered material was cut to predetermined dimensions by
wire discharge cutting, each being brazed onto a mounting seat of a
cemented carbide substrate, thereby to make a throwaway cutting
tool having the configuration specified in JIS CNGA120408.
[0210] The measurement of residual stress of the tool tip made as
described above showed residual compressive stresses of
.sigma..sub.cBN=535 MPa, .sigma..sub.TiC=120 MPa and
.sigma..sub.TiN=220 MPa. The cutting tool was subjected to cutting
tests similarly to Example I. The samples experienced the amount of
wear as small as 0.16 mm after cutting for 20 minutes, showed no
chipping after being subjected to 60000 impacts in interrupted
cutting test, thus exhibiting excellent cutting performance.
EXAMPLE IX
[0211] A cBN material powder having a mean particle size of 1.5
.mu.m, a TiC material powder having a mean particle size of 1
.mu.m, a TiN material powder having a mean particle size of 1
.mu.m, a TiCN material powder having a mean particle size of 1
.mu.m, a HfC material powder having a mean particle size of 1
.mu.m, a NbC material powder having a mean particle size of 1
.mu.m, a metal Al powder having a mean particle size of 1.2 .mu.m
and a metal Co powder having a mean particle size of 0.8 .mu.m were
prepared in proportions shown in Table 9, and were mixed in a ball
mill using alumina balls for 16 hours.
[0212] The mixed powder was press formed under a pressure of 98
MPa. This green compact was fired while maintaining a pressure of 5
GPa and a temperature of 1400.degree. C. for 15 minutes in an
ultra-high pressure, high temperature apparatus, thereby to obtain
the cBN sintered material (samples Nos. IX-1 to 9 shown in Table
9). TABLE-US-00009 TABLE 9 Firing condition Temperature Firing
Firing Temperature Sample Proportion (% by volume) raising rate
temperature period lowering rate No..sup.1) cBN Carbide Nitride
Metal Others (.degree. C./min.) (.degree. C.) (minute) (.degree.
C./min.) .sup. IX-1 the rest TiC: 20 TiN: 25 Al: 10 -- 50 1400 15
50 .sup. IX-2 the rest TiC: 8 TiN: 18 Al: 5 -- 35 1400 15 35 WC: 4
Co: 3 .sup. IX-3 the rest HfC: 23 TiN: 8 Al: 13 -- 40 1400 15 40
.sup. IX-4 the rest TiC: 5 TiN: 10 Al: 10 -- 45 1400 15 45 Co: 5
.sup. IX-5 the rest TiC: 8 TiN: 10 Al: 14 -- 50 1420 15 50 * IX-6
the rest TiC: 45 -- Al: 15 -- 35 1375 15 35 * IX-7 the rest -- TiN:
35 Al: 15 -- 45 1300 30 45 * IX-8 the rest -- -- Al: 8 TiCN: 30 50
1400 15 50 * IX-9 the rest TiC: 21 TiN: 3 Al: 3 -- 40 1500 15 40
NbC: 10 Co: 3 .sup.1)Samples marked `*` are out of the scope of the
present invention.
[0213] The samples of the cBN sintered material were cut by wire
discharge cutting or the like into shape specified in JIS
CNGA120408, each being brazed onto a mounting seat of a cemented
carbide substrate. Each tool tip of the cBN sintered material that
was brazed was coated with a hard film according to the composition
and film forming method shown in Table 11, thereby to make
throwaway cutting tool made of the cBN sintered material coated
with the hard film (surface-coated cBN sintered material). The hard
film was formed by ion plating method at temperature of 500.degree.
C. with bias voltage of 150 V.
[0214] The cutting tools obtained as described above were evaluated
for the contents of components, peak diffraction intensity, film
thickness, ratio [I.sub.(111)/I.sub.(200)], residual compressive
stress, continuous cutting test and interrupted cutting test, by
the methods as follows. The results of measuring the contents of
components and peak diffraction intensity are shown in Table 10,
and the results of measuring film thickness, ratio
[I.sub.(111)/I.sub.(200)], residual compressive stress, continuous
cutting test and interrupted cutting test are shown in Table
11.
(Contents of Components)
[0215] Contents of components in each of the cutting tools were
determined through observation of the structure under a
metallurgical microscope similarly to Example I.
[0216] As to carbonitride, the presence was determined by the X-ray
diffraction peak. When the peak was observed, peak of carbide, peak
of nitride and peak of carbonitride were quantified through peak
separation, and the content of carbonitride was calculated from the
proportions of the peak intensities.
(Intensities of a Diffraction Peaks)
[0217] X-ray diffraction analysis was conducted similarly to
Example III. From the diffraction chart, normalized peak
intensities I.sub.C, I.sub.N, I.sub.IL, and I.sub.CN were
calculated assuming I.sub.cBN to be 100.
(Thickness of Hard Film)
[0218] Thickness of the hard film was measured by observing the
rupture surface of the surface-coated cBN sintered material under a
scanning electron microscope.
(Ratio [I.sub.(111)/I.sub.(200)] of X-ray diffraction peaks of hard
film)
[0219] Intensity I.sub.(111) of a Diffraction Peak Attributed to
(111) plane and intensity I.sub.(200) of a diffraction peak
attributed to (200) plane of the hard film were measured by X-ray
diffraction analysis, and the ratio [I.sub.(111)/I.sub.(200)] was
calculated.
(Residual Compressive Stress of cBN Sintered Material)
[0220] Residual stresses acting on the cBN particles and on the
hard film were determined similarly to Example VII. In the case of
hard film constituted from a plurality of layers, the residual
stress of the thickest layer of the hard film was measured.
(Cutting Test)
[0221] Continuous cutting test and interrupted cutting test were
conducted similarly to Example I, except for setting the limit for
the number of impacts experienced before chipping in the
interrupted cutting test to 60000 instead of 40000. TABLE-US-00010
TABLE 10 Content proportion in sintered material.sup.2) (% by area)
Sample Intermediate Proportion of X-ray peak intensity in sintered
material.sup.3) No..sup.1) cBN Carbide Nitride phase Carbonitride
I.sub.cBN I.sub.C I.sub.N I.sub.IL I.sub.CN I.sub.C/I.sub.N
I.sub.IL/I.sub.cBN .sup. IX-1 44 18 25 11 2 100 44 79 63 2 0.56
0.63 .sup. IX-2 51 17 15 16 1 100 53 67 77 12 0.79 0.77 .sup. IX-3
71 18 6 5 -- 100 33 51 10 -- 0.65 0.10 .sup. IX-4 77 3 7 13 -- 100
19 86 42 -- 0.22 0.42 .sup. IX-5 65 10 19 4 2 100 26 65 27 5 0.40
0.27 * IX-6 45 38 -- 13 3 100 87 -- 32 8 -- 0.32 * IX-7 52 -- 35 17
-- 100 -- 70 56 -- -- 0.56 * IX-8 60 -- -- 15 25 100 -- -- 51 41 --
0.51 * IX-9 62 22 -- 2 14 100 27 -- 9 38 -- 0.09 .sup.1)Samples
marked `*` are out of the scope of the present invention.
.sup.2)Content proportion: cBN particles, carbide and nitride were
observed under a metallurgical microscope, The content of
carbonitride was calculated from XRD peak. .sup.3)Proportion of
X-ray diffraction peak intensity in sintered materia I.sub.cBN: cBN
(111) plane diffraction peak, , I.sub.N: Nitride (200) plane
diffraction peak, I.sub.C: Carbide (200) plane diffraction peak,
I.sub.IL: Intermediate phase (101) plane diffraction peak,
I.sub.CN: Carbonitride (200) plane diffraction peak
[0222] TABLE-US-00011 TABLE 11 Residual compressive Continuous
Interrupted stress.sup.4) cutting cutting Hard coating.sup.2)3)
Coating test test Sample Coating cBN (film) Amount of Number of
No..sup.1) First layer Second layer Third layer Fourth layer method
(MPa) (GPa) wear (mm) impacts .sup. IX-1 (Ti.sub.0.5, Al.sub.0.5)N
-- -- -- Ion plating 500 2.2 0.12 50000 (1.7)[1.5] .sup. IX-2 TiN
TiCN Al.sub.2O.sub.3 TiN Thermal CVD 900 -0.3 0.10 39000 (0.1)[3.1]
(6.0)[0.7] (3.0)[--] (0.1)[2.2] .sup. IX-3 Ti TiN -- -- Ion plating
600 1.2 0.13 40000 (0.1)[--] (1.5)[2.0] .sup. IX-4 TiN (Ti.sub.0.2,
Al.sub.0.7Cr.sub.0.1)N -- -- Ion plating 400 0.9 0.14 45000
(0.1)[2.0] (1.0)[1.0] .sup. IX-5 TiCN -- -- -- Sputtering 250 1.4
0.18 40000 (1.8)[1.2] * IX-6 (Ti.sub.0.5, Al.sub.0.5)N TiN -- --
Ion plating 150 1.2 0.21 13000 (2.0)[0.8] (0.2)[1.7] * IX-7 TiN --
-- -- Ion plating 160 1.3 0.23 8500 (1.0)[2.0] * IX-8 TiCN -- -- --
Ion plating 200 2 0.20 12000 (2.5)[0.9] * IX-9 -- -- -- -- -- 150
-- 0.31 28000 .sup.1)Samples marked `*` are out of the scope of the
present invention. .sup.2)Figures in round brackets ( ) stand for a
film thickness of hard film. (unit: .mu.m) .sup.3)Figures in square
brackets [ ] stand for a ratio [I.sub.(111)/I.sub.(200)] of the
(111) plane peak intensity to the (200) plane peak intensity in
XRD. .sup.4)The figure with a minus sign stands for tensile
residual stress.
[0223] The results shown in Tables 9 to 11 indicate that samples
Nos. IX-6 and 9, wherein the sintered material contained only
carbide (TiC), had weak binding between the cBN particles, and were
therefore insufficient in chipping resistance. Sample No. IX-7,
wherein the sintered material contained only nitride (TiN), had
insufficient wear resistance and short service life. Sample No.
IX-8, wherein carbonitride (TiCN) was used as the binder phase, was
insufficient in both wear resistance and chipping resistance.
Sample No. IX-9, wherein hard film was not provided, was
insufficient in both wear resistance and chipping resistance.
[0224] Samples Nos. IX-1 to 5 that were within the scope of the
present invention, all had sufficient wear resistance with the
amount of wear not larger than 0.20 mm in continuous cutting of
carburizing-hardened steel, that is a hard-to-cut material, and
endured 35000 or more impacts before chipping in the interrupted
cutting test. Sample No. IX-1, in particular, showed no chipping
after experiencing 50000 impacts, thus exhibited excellent chipping
resistance and demonstrated stable cutting performance over an
extended period of time.
EXAMPLE X
[0225] The green compact of core member was made by extrusion
molding of a powder material that was prepared by mixing 50% by
volume of cBN, 35% by volume of TiN and 15% by volume of Al and
adding an organic binder thereto. The green compact of shell member
was made by extrusion molding of a material that was prepared by
mixing 65% by volume of cBN, 25% by volume of TiC and 10% by volume
of Al and adding an organic binder thereto.
[0226] The green compact of core member and the green compact of
shell member made as described above were used to form composite
green compact of multi-filament structure similarly to Example II
and were fired thereby to make a composite cBN sintered
material.
[0227] The samples of the cBN sintered material were cut by wire
discharge cutting into predetermined dimensions (shape specified in
JIS CNGA120408), each being brazed onto a mounting seat of a
cemented carbide substrate. The cBN sintered material that was
brazed was coated with (Ti.sub.0.5, Al.sub.0.5)N film to a
thickness of 2.0 .mu.m on the surface thereof by cathode arc ion
plating, thereby to make a cutting tool (sample No. X-1) made of
the surface-coated cBN sintered material.
[0228] The structure of the cutting tool thus obtained was observed
under a metallurgical microscope. The cBN particles appearing in
black, TiC appearing in brown and TiN appearing in white were
clearly distinguished. Areas of 30 grains of each component were
measured by image analysis and were averaged. Proportions of the
areas occupied by the components were calculated through comparison
of these mean values, with the results of 50% for cBN, 10% for TiC,
25% for TiN and 2% for TiCN.
[0229] Through X-ray diffraction analysis (XRD) of the hard film of
the cutting tool described above, intensity I.sub.(111) of a
diffraction peak attributed to (111) plane and intensity
I.sub.(200) of a diffraction peak attributed to (200) plane were
measured similarly to Example IX, and the ratio
[I.sub.(111)/I.sub.(200)] was determined to be 1.8.
[0230] The sample was subjected to cutting test similarly to
Example IX, in which it experienced the amount of wear as small as
0.15 mm after cutting for 20 minutes, and showed no chipping after
being subjected to 60000 impacts in the interrupted cutting test,
thus exhibiting excellent cutting performance.
EXAMPLE XI
[0231] The same cBN sintered material as that of sample No. IX-1
shown in Table 9 was made by a method similar to that of Example
IX. The cBN sintered material was cut by wire discharge cutting
into predetermined shape and was brazed onto a mounting seat of a
throwaway tool tip made of cemented carbide of milling cutter, thus
making a cutting tool similarly to Example IX except for forming a
diamond-like carbon film having thickness of 0.2 .mu.m by plasma
CVD process (sample No. XI-1).
[0232] The same cBN sintered material as that of sample No. IX-8
shown in Table 9 was made. The cBN sintered material was cut by
wire discharge cutting into predetermined shape and was brazed onto
a mounting seat of a throwaway tool tip made of cemented carbide of
milling cutter, thus making a cutting tool similarly to Example IX
except for forming a diamond-like carbon film having thickness of
0,2 .mu.m by plasma CVD process (sample No. XI-2).
[0233] The cutting tools made as described above were subjected to
cutting performance test under the following conditions. [0234]
Mode of cutting: Milling [0235] Workpiece: Ti-16Al-4V alloy [0236]
Cutting speed: 500 m/min. [0237] Infeed: 1.0 mm [0238] Feed rate:
0.3 mm/blade [0239] Measurement: Condition of cutting edge was
observed by a scanning electron microscope when the length of
cutting reached 1 m.
[0240] In the cutting test, sample No. XI-2 was damaged on the
cutting edge that showed chipping and peel-off of the film, while
sample No. XI-1 remained sound with the cutting edge showing no
chipping nor peel-off of the film.
* * * * *